NEET (UG) · 2023

NEET 2023, question by question

Which chapter each question came from, how the paper was spread, and how to solve each one. Keep the official paper open beside this page.

Sit this paper free All years, chapter-wise

Summary

The heaviest chapters in each subject, and how the questions were spread by level. One year is not a forecast.

Physics
50 Q
1. Current Electricity5
2. Kinematics5
3. Electrostatics4
38 easy · 10 medium · 2 hard
Chemistry
50 Q
1. p-Block Elements4
2. Chemical Bonding and Molecular Structure4
3. Haloalkanes and Haloarenes3
36 easy · 13 medium · 1 hard
Botany
58 Q
1. Molecular Basis of Inheritance8
2. Cell Cycle and Cell Division6
3. Principles of Inheritance and Variation5
43 easy · 14 medium · 1 hard
Zoology
42 Q
1. Biotechnology: Principles and Processes5
2. Biomolecules4
3. Animal Kingdom4
31 easy · 11 medium · 0 hard

Chapters

Every chapter asked, and the NCERT chapters to read for it.

Molecular Basis of Inheritance8
Class 12: Molecular Basis of Inheritance
Cell Cycle and Cell Division6
Class 11: Cell Cycle and Cell Division
Principles of Inheritance and Variation5
Class 12: Principles of Inheritance and Variation
Environmental Issues4
No matching NCERT chapter
Organisms and Populations4
Class 12: Organisms and Populations
Plant Kingdom3
Class 11: Plant Kingdom
Sexual Reproduction in Flowering Plants3
Class 12: Sexual Reproduction in Flowering Plants
Cell: The Unit of Life3
Class 11: Cell: The Unit of Life
Plant Growth and Development3
Class 11: Plant Growth and Development
Morphology of Flowering Plants3
Class 11: Morphology of Flowering Plants
Photosynthesis in Higher Plants3
Class 11: Photosynthesis in Higher Plants
Anatomy of Flowering Plants3
Class 11: Anatomy of Flowering Plants
Biodiversity and Conservation2
Class 12: Biodiversity and Conservation
Mineral Nutrition2
No matching NCERT chapter
Transport in Plants2
No matching NCERT chapter
Ecosystem2
Class 12: Ecosystem
Respiration in Plants2
Class 11: Respiration in Plants

Questions

Tap Explain on any question for a short summary and our full working.

Physics questions, each with its chapter and our explanation
Q	Chapter and topic	NCERT	Kind and level
1	Properties of Bulk MatterElasticity	Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter	Single correctEasy
A easy single correct question on elasticity, from Properties of Bulk Matter. NCERT: Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter The wire is light, so the tension is the same everywhere along it and equals the hanging weight: $T = W$. Longitudinal stress is the internal restoring force per unit area of the cross-section: $\sigma = \frac{T}{A} = \frac{W}{A}$. (The forces $W$ pulling on either side of a cross-section are a pair; they are not added to make $2W$.) Answer: (2) $W/A$.
2	Motion of System of Particles and Rigid BodyMoment of inertia	Class 11: Systems of Particles and Rotational Motion	Single correctEasy
A easy single correct question on moment of inertia, from Motion of System of Particles and Rigid Body. NCERT: Class 11: Systems of Particles and Rotational Motion Radius of gyration: $I = Mk^2$. Solid sphere about a diameter: $I_1 = \frac{2}{5}MR^2$, so $k_1^2 = \frac{2}{5}R^2$. Thin hollow sphere about a diameter: $I_2 = \frac{2}{3}MR^2$, so $k_2^2 = \frac{2}{3}R^2$. $\frac{k_1^2}{k_2^2} = \frac{2/5}{2/3} = \frac{3}{5}$, so $\frac{k_1}{k_2} = \sqrt{3} : \sqrt{5}$. The options do not carry square roots; the only option matching the comparison is 3 : 5, which is the ratio of the squares of the radii of gyration (equally, the ratio of the moments of inertia). Answer: (1) 3 : 5.
3	ElectrostaticsCapacitance	Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance	Single correctEasy
A easy single correct question on capacitance, from Electrostatics. NCERT: Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance The two $3\ \mu F$ capacitors on the right are in parallel: $C_p = 3 + 3 = 6\ \mu F$. This is in series with the $3\ \mu F$ capacitor next to $A$: $\frac{1}{C} = \frac{1}{3} + \frac{1}{6} = \frac{1}{2}$, so $C = 2\ \mu F$. Answer: (1) $2\ \mu F$.
4	Laws of MotionNewton's laws	Class 11: Laws of Motion	Single correctEasy
A easy single correct question on newton's laws, from Laws of Motion. NCERT: Class 11: Laws of Motion The force is along the change in momentum, $\Delta\vec{v} = \vec{v}_f - \vec{v}_i$. Take east $= \hat{i}$, north $= \hat{j}$. Initially $\vec{v}_i = -v\hat{j}$ (south), finally $\vec{v}_f = v\hat{i}$ (east). $\Delta\vec{v} = v\hat{i} - (-v\hat{j}) = v\hat{i} + v\hat{j}$, which points equally east and north: north-east. Answer: (3) along north-east.
5	ElectrostaticsGauss's law	Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance	Single correctEasy
A easy single correct question on gauss's law, from Electrostatics. NCERT: Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance Zero net flux through a closed surface means the outward flux equals the inward flux: as many field lines leave the surface as enter it (by Gauss's law, the net enclosed charge is zero). It says nothing about the field being constant in magnitude on the surface (2) or uniform inside (4); and the charges producing the field may well be outside the surface (3) — indeed zero flux is what an outside charge gives. Answer: (1).
6	Work, Energy and PowerConservation of energy	Class 11: Work, Energy and Power	Single correctEasy
A easy single correct question on conservation of energy, from Work, Energy and Power. NCERT: Class 11: Work, Energy and Power Spring potential energy $U = \frac{1}{2}kx^2 \propto x^2$. $\frac{U'}{U} = \left(\frac{8}{2}\right)^2 = 16$, so $U' = 16U$. Answer: (4) 16U.
7	Current ElectricityKirchhoff's rules	Class 12: Current Electricity	Single correctMedium
A medium single correct question on kirchhoff's rules, from Current Electricity. NCERT: Class 12: Current Electricity With no current through $G$, the branch holding $G$ and the 2 V cell carries no current, so the 10 V cell drives one current $I$ through $400\ \Omega$ and $R$ in series: $I = \frac{10}{400 + R}$. The 2 V cell (with no current, so no drop across $G$) is connected directly across $R$, so the potential difference across $R$ must equal 2 V: $IR = \frac{10R}{400 + R} = 2 \Rightarrow 10R = 800 + 2R \Rightarrow R = 100\ \Omega$. Check: $I = 10/500 = 0.02$ A; drop across $400\ \Omega$ is 8 V and across $R$ is 2 V, total 10 V. Answer: (3) $100\ \Omega$.
8	Electromagnetic Induction and Alternating CurrentsTransformers	Class 12: Electromagnetic Induction; Class 12: Alternating Current	Single correctEasy
A easy single correct question on transformers, from Electromagnetic Induction and Alternating Currents. NCERT: Class 12: Electromagnetic Induction; Class 12: Alternating Current An ideal transformer delivers the same power in the primary as in the secondary: $V_pI_p = 60$ W. $I_p = \frac{60}{220} = 0.273$ A $\approx 0.27$ A. Second way: $I_s = 60/12 = 5$ A, and $I_p = I_s\frac{V_s}{V_p} = 5 \times \frac{12}{220} = 0.27$ A. Answer: (1) 0.27 A.
9	Electronic DevicesRectifiers	Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits	Single correctEasy
A easy single correct question on rectifiers, from Electronic Devices. NCERT: Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits The diodes rectify (make the output unidirectional), the centre-tapped transformer supplies the two half-voltages, and the load uses the output. The capacitor across the load is the filter: it charges at the peaks and discharges slowly between them, smoothing the ripple. Answer: (3) Capacitor.
10	OpticsTotal internal reflection and prisms	Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics	Single correctMedium
A medium single correct question on total internal reflection and prisms, from Optics. NCERT: Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics Speed in air $c = \frac{x}{t_1}$; speed in the medium $v = \frac{10x}{t_2}$. Refractive index $n = \frac{c}{v} = \frac{x/t_1}{10x/t_2} = \frac{t_2}{10\,t_1}$. Critical angle: $\sin C = \frac{1}{n} = \frac{10\,t_1}{t_2}$, so $C = \sin^{-1}\left(\frac{10\,t_1}{t_2}\right)$. Answer: (4).
11	Current ElectricityResistivity	Class 12: Current Electricity	Single correctEasy
A easy single correct question on resistivity, from Current Electricity. NCERT: Class 12: Current Electricity $22000\ \Omega = 22 \times 10^3\ \Omega$. First band: 2 (red); second band: 2 (red); third band, the multiplier $10^3$: orange (black 0, brown 1, red 2, orange 3). The fourth band, gold, is the $\pm 5\%$ tolerance. Answer: (3) Orange.
12	Electronic DevicesSpecial-purpose diodes	Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits	StatementsEasy
A easy statements question on special-purpose diodes, from Electronic Devices. NCERT: Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits Statement I: a photovoltaic device (a solar cell) generates an emf when light falls on it — it converts optical radiation into electrical energy. Correct. Statement II: a Zener diode is heavily doped and is meant to be used in reverse bias in the breakdown region, where the voltage across it stays nearly constant (voltage regulation). Correct. Answer: (1).
13	Electromagnetic Induction and Alternating CurrentsSelf and mutual inductance	Class 12: Electromagnetic Induction; Class 12: Alternating Current	Single correctEasy
A easy single correct question on self and mutual inductance, from Electromagnetic Induction and Alternating Currents. NCERT: Class 12: Electromagnetic Induction; Class 12: Alternating Current $U = \frac{1}{2}LI^2 = \frac{1}{2} \times 4 \times 10^{-6} \times 2^2 = 8 \times 10^{-6}$ J $= 8\ \mu J$. Answer: (4).
14	KinematicsUniform circular motion	Class 11: Motion in a Straight Line; Class 11: Motion in a Plane	Single correctEasy
A easy single correct question on uniform circular motion, from Kinematics. NCERT: Class 11: Motion in a Straight Line; Class 11: Motion in a Plane Angular velocity $\vec{\omega}$ of a body moving on a circle points along the axis of rotation (right-hand rule). Its rate of change, the angular acceleration $\vec{\alpha} = \frac{d\vec{\omega}}{dt}$, therefore also lies along the axis (the axis does not change direction). The radial and tangential directions belong to the linear (centripetal and tangential) accelerations, not the angular one. Answer: (4).
15	ThermodynamicsSecond law	Class 11: Thermodynamics	Single correctEasy
A easy single correct question on second law, from Thermodynamics. NCERT: Class 11: Thermodynamics $\eta = 1 - \frac{T_2}{T_1}$ with temperatures in kelvin. $T_1 = 327 + 273 = 600$ K. $0.5 = 1 - \frac{T_2}{600} \Rightarrow T_2 = 300$ K $= 27°$ C. Answer: (1).
16	GravitationGravitational potential energy	Class 11: Gravitation	Single correctMedium
A medium single correct question on gravitational potential energy, from Gravitation. NCERT: Class 11: Gravitation Let the field vanish at distance $x$ from $m$: $\frac{Gm}{x^2} = \frac{G(9m)}{(R-x)^2} \Rightarrow R - x = 3x \Rightarrow x = \frac{R}{4}$. The point is $\frac{R}{4}$ from $m$ and $\frac{3R}{4}$ from $9m$. Potential (a scalar sum): $V = -\frac{Gm}{R/4} - \frac{G(9m)}{3R/4} = -\frac{4Gm}{R} - \frac{12Gm}{R} = -\frac{16Gm}{R}$. Answer: (3).
17	KinematicsMotion in a straight line	Class 11: Motion in a Straight Line; Class 11: Motion in a Plane	Single correctEasy
A easy single correct question on motion in a straight line, from Kinematics. NCERT: Class 11: Motion in a Straight Line; Class 11: Motion in a Plane Let the whole distance be $2d$. Time: $t = \frac{d}{\vartheta} + \frac{d}{2\vartheta} = \frac{3d}{2\vartheta}$. Average speed $= \frac{2d}{3d/(2\vartheta)} = \frac{4\vartheta}{3}$. (For equal distances it is the harmonic mean $\frac{2v_1v_2}{v_1+v_2} = \frac{2 \cdot \vartheta \cdot 2\vartheta}{3\vartheta} = \frac{4\vartheta}{3}$.) Answer: (3).
18	Properties of Bulk MatterSurface tension	Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter	Single correctEasy
A easy single correct question on surface tension, from Properties of Bulk Matter. NCERT: Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter A soap bubble has two surfaces (inside and outside), so the new surface area is $2 \times 4\pi r^2$. $W = T \times 8\pi r^2 = 0.03 \times 8\pi \times (0.02)^2 = 0.03 \times 8\pi \times 4 \times 10^{-4} = 9.6\pi \times 10^{-5}$ J $\approx 3.02 \times 10^{-4}$ J. Answer: (3) $3.01 \times 10^{-4}$ J (nearly).
19	Dual Nature of Matter and RadiationPhotoelectric effect	Class 12: Dual Nature of Radiation and Matter	Single correctEasy
A easy single correct question on photoelectric effect, from Dual Nature of Matter and Radiation. NCERT: Class 12: Dual Nature of Radiation and Matter The shortest wavelength is emitted when the electron's entire kinetic energy $eV$ goes into one photon: $eV = \frac{hc}{\lambda_{min}}$. $\lambda_{min} = \frac{hc}{eV} \propto \frac{1}{V}$. Answer: (2).
20	Atoms and NucleiRadioactivity	Class 12: Atoms; Class 12: Nuclei	Single correctEasy
A easy single correct question on radioactivity, from Atoms and Nuclei. NCERT: Class 12: Atoms; Class 12: Nuclei $\frac{A}{A_0} = \left(\frac{1}{2}\right)^{n}$ after $n$ half-lives. $\frac{1}{16} = \left(\frac{1}{2}\right)^4$, so $n = 4$. Time $= 4 \times 20 = 80$ minutes. Answer: (4).
21	Physical World and MeasurementError analysis	Class 11: Units and Measurement	Single correctEasy
A easy single correct question on error analysis, from Physical World and Measurement. NCERT: Class 11: Units and Measurement $\rho = \frac{m}{\pi r^2 L}$, so $\frac{\Delta\rho}{\rho} = \frac{\Delta m}{m} + 2\frac{\Delta r}{r} + \frac{\Delta L}{L}$. $\frac{\Delta m}{m} = \frac{0.002}{0.4} = 0.5\%$; $2\frac{\Delta r}{r} = 2 \times \frac{0.001}{0.3} = 0.667\%$; $\frac{\Delta L}{L} = \frac{0.02}{5} = 0.4\%$. Total $= 0.5 + 0.667 + 0.4 = 1.567\% \approx 1.6\%$. Answer: (3).
22	Electromagnetic WavesProperties of electromagnetic waves	Class 12: Electromagnetic Waves	Single correctEasy
A easy single correct question on properties of electromagnetic waves, from Electromagnetic Waves. NCERT: Class 12: Electromagnetic Waves In an electromagnetic wave $B_0 = \frac{E_0}{c} = \frac{48}{3 \times 10^8} = 1.6 \times 10^{-7}$ T. The frequency is not needed. Answer: (3).
23	Behaviour of Perfect Gas and Kinetic TheoryKinetic theory	Class 11: Kinetic Theory	Single correctMedium
A medium single correct question on kinetic theory, from Behaviour of Perfect Gas and Kinetic Theory. NCERT: Class 11: Kinetic Theory $v_{rms} = \sqrt{\frac{3RT}{M}} \propto \sqrt{T}$. Initial temperature $T_1 = -50 + 273 = 223$ K. "Increased by 3 times" means the speed increases by $3v$, becoming $v + 3v = 4v$: $\frac{T_2}{T_1} = 4^2 = 16 \Rightarrow T_2 = 16 \times 223 = 3568$ K $= 3568 - 273 = 3295°$ C. (Had the speed only become 3 times, $T_2 = 9 \times 223 = 2007$ K $= 1734°$ C, which is not offered.) Answer: (2) 3295° C.
24	Electromagnetic WavesDisplacement current	Class 12: Electromagnetic Waves	Single correctEasy
A easy single correct question on displacement current, from Electromagnetic Waves. NCERT: Class 12: Electromagnetic Waves Capacitive reactance $X_C = \frac{1}{2\pi fC}$: when $f$ decreases, $X_C$ increases, so (1) and (4) are wrong. The current in the circuit $I = \frac{V}{X_C} = 2\pi fCV$ falls. Between the plates this current exists as the displacement current (equal to the conduction current), so the displacement current decreases. Answer: (3).
25	OpticsInterference and diffraction	Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics	StatementsEasy
A easy statements question on interference and diffraction, from Optics. NCERT: Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics Angular fringe separation $\theta = \frac{\lambda}{d}$. Statement I: it does not involve the screen distance $D$ (the linear width $\beta = \frac{\lambda D}{d}$ grows, the angle does not). True. Statement II: a larger $\lambda$ gives a larger angular separation, not smaller. False. Answer: (3).
26	Atoms and NucleiHydrogen spectrum	Class 12: Atoms; Class 12: Nuclei	Single correctEasy
A easy single correct question on hydrogen spectrum, from Atoms and Nuclei. NCERT: Class 12: Atoms; Class 12: Nuclei The shortest wavelength of a series is the series limit, $n_2 \to \infty$: $\frac{1}{\lambda} = \frac{R}{n_1^2}$. Balmer ($n_1 = 2$): $\lambda = \frac{4}{R}$. Brackett ($n_1 = 4$): $\lambda' = \frac{16}{R}$. $\lambda' = 4\lambda$. Answer: (2).
27	Dual Nature of Matter and RadiationPhotoelectric effect	Class 12: Dual Nature of Radiation and Matter	Single correctEasy
A easy single correct question on photoelectric effect, from Dual Nature of Matter and Radiation. NCERT: Class 12: Dual Nature of Radiation and Matter Photoemission needs photon energy at least equal to the work function. 2.20 eV > 2.14 eV (Cs): emits. 2.20 eV < 2.30 eV (K) and < 2.75 eV (Na): no emission. Answer: (1) Cs only.
28	Physical World and MeasurementError analysis	Class 11: Units and Measurement	Single correctEasy
A easy single correct question on error analysis, from Physical World and Measurement. NCERT: Class 11: Units and Measurement Errors that occur irregularly, with random sign and size, because of unpredictable fluctuations in experimental conditions (temperature, supply voltage, mechanical vibration) are random errors. Instrumental and personal errors are systematic; least count errors come from the resolution of the instrument. Answer: (4).
29	Electromagnetic Induction and Alternating CurrentsLCR circuits and resonance	Class 12: Electromagnetic Induction; Class 12: Alternating Current	Single correctEasy
A easy single correct question on lcr circuits and resonance, from Electromagnetic Induction and Alternating Currents. NCERT: Class 12: Electromagnetic Induction; Class 12: Alternating Current $\omega_0 = \frac{1}{\sqrt{LC}} = \frac{1}{\sqrt{10^{-2} \times 10^{-6}}} = \frac{1}{10^{-4}} = 10^4$ rad/s. $f_0 = \frac{\omega_0}{2\pi} = \frac{10^4}{6.283} \approx 1592$ Hz $= 1.59$ kHz. Answer: (4).
30	Properties of Bulk MatterFluid mechanics	Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter	Single correctEasy
A easy single correct question on fluid mechanics, from Properties of Bulk Matter. NCERT: Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter A venturi-meter measures flow speed from the pressure drop at its narrow throat: where the fluid speeds up (continuity) the pressure falls, as Bernoulli's principle $P + \frac{1}{2}\rho v^2 = $ constant requires. Answer: (2).
31	Oscillations and WavesStanding waves and beats	Class 11: Oscillations; Class 11: Waves	Single correctEasy
A easy single correct question on standing waves and beats, from Oscillations and Waves. NCERT: Class 11: Oscillations; Class 11: Waves Open pipe fundamental: $f_o = \frac{v}{2L}$. Closed pipe fundamental: $f_c = \frac{v}{4L}$. $\frac{f_o}{f_c} = \frac{4L}{2L} = 2 : 1$. Answer: (2).
32	ElectrostaticsElectric dipole	Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance	Single correctEasy
A easy single correct question on electric dipole, from Electrostatics. NCERT: Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance $\tau = pE\sin\theta = (q \cdot 2a)E\sin\theta$. $4 = q \times 0.02 \times 2 \times 10^5 \times \sin 30° = q \times 2000$. $q = 2 \times 10^{-3}$ C $= 2$ mC. Answer: (4).
33	Current ElectricityKirchhoff's rules	Class 12: Current Electricity	Single correctMedium
A medium single correct question on kirchhoff's rules, from Current Electricity. NCERT: Class 12: Current Electricity From the drawing, the 10 V cell has its positive (long) plate towards $E$ and the 5 V cell also has its positive plate towards $E$: the two cells oppose each other. Net emf $= 10 - 5 = 5$ V, acting in the sense of the 10 V cell. Total resistance $= 2 + 1 + 7 = 10\ \Omega$. $I = \frac{5}{10} = 0.5$ A. The 10 V cell pushes current out of its positive plate, towards $E$, so in the top branch the current goes $A \to$ 10 V cell $\to E \to$ 5 V cell $\to B$, and returns through $C$, $D$ and the $7\ \Omega$ resistor. Answer: (2) 0.5 A from $A$ to $B$ through $E$.
34	Magnetic Effects of Current and MagnetismMagnetic dipole	Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter	Single correctEasy
A easy single correct question on magnetic dipole, from Magnetic Effects of Current and Magnetism. NCERT: Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter Gauss's law for magnetism: $\oint \vec{B}\cdot d\vec{S} = 0$. There are no isolated magnetic poles; magnetic field lines are closed loops, so every line entering a closed surface also leaves it. Answer: (1) Zero.
35	KinematicsProjectile motion	Class 11: Motion in a Straight Line; Class 11: Motion in a Plane	Single correctEasy
A easy single correct question on projectile motion, from Kinematics. NCERT: Class 11: Motion in a Straight Line; Class 11: Motion in a Plane $H = \frac{u^2\sin^2\theta}{2g} = \frac{(280 \times 0.5)^2}{2 \times 9.8} = \frac{140^2}{19.6} = \frac{19600}{19.6} = 1000$ m. Answer: (3).
36	OpticsLenses and mirrors	Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics	Single correctEasy
A easy single correct question on lenses and mirrors, from Optics. NCERT: Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics $\frac{1}{F} = \frac{1}{f} + \frac{1}{-f} = 0$, so $F = \infty$: the combination acts as a plane glass plate. Answer: (4) Infinite.
37	Electromagnetic Induction and Alternating CurrentsLCR circuits and resonance	Class 12: Electromagnetic Induction; Class 12: Alternating Current	Single correctMedium
A medium single correct question on lcr circuits and resonance, from Electromagnetic Induction and Alternating Currents. NCERT: Class 12: Electromagnetic Induction; Class 12: Alternating Current The inductor $\frac{50}{\pi}$ mH, the capacitor $\frac{10^3}{\pi}\ \mu F$ and the $10\ \Omega$ resistor are in series across 220 V, 50 Hz. $X_L = 2\pi fL = 2\pi \times 50 \times \frac{50}{\pi} \times 10^{-3} = 5\ \Omega$. $X_C = \frac{1}{2\pi fC} = \frac{1}{2\pi \times 50 \times \frac{10^3}{\pi} \times 10^{-6}} = \frac{1}{0.1} = 10\ \Omega$. $Z = \sqrt{R^2 + (X_C - X_L)^2} = \sqrt{100 + 25} = \sqrt{125} = 5\sqrt{5}\ \Omega$. Answer: (3).
38	Oscillations and WavesSHM	Class 11: Oscillations; Class 11: Waves	Single correctMedium
A medium single correct question on shm, from Oscillations and Waves. NCERT: Class 11: Oscillations; Class 11: Waves From the graph: amplitude $A = 1$ m, $x = 0$ at $t = 0$ rising, $x = 1$ m at $t = 2$ s, back to 0 at 4 s, $-1$ m at 6 s, 0 at 8 s. Period $T = 8$ s, so $\omega = \frac{2\pi}{8} = \frac{\pi}{4}$ rad/s and $x = \sin\left(\frac{\pi t}{4}\right)$. At $t = 2$ s, $x = 1$ m (the positive extreme). $a = -\omega^2 x = -\frac{\pi^2}{16} \times 1 = -\frac{\pi^2}{16}$ m s$^{-2}$. Answer: (4).
39	ElectrostaticsElectric field and potential	Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance	Single correctMedium
A medium single correct question on electric field and potential, from Electrostatics. NCERT: Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance From the figure: $-q$ is 3 cm to the left of O, $+q$ is 3 cm to the right of O, and P is on the axis 5 cm from O. Distance of P from $+q$: $5 - 3 = 2$ cm $= 0.02$ m; from $-q$: $5 + 3 = 8$ cm $= 0.08$ m. $V = Kq\left(\frac{1}{0.02} - \frac{1}{0.08}\right) = Kq(50 - 12.5) = 37.5\,Kq = \frac{3}{8} \times 10^2\,Kq$. In units of $10^2$ V: $\left(\frac{3}{8}\right)qK$. Answer: (1).
40	KinematicsMotion in a straight line	Class 11: Motion in a Straight Line; Class 11: Motion in a Plane	Single correctMedium
A medium single correct question on motion in a straight line, from Kinematics. NCERT: Class 11: Motion in a Straight Line; Class 11: Motion in a Plane Assume a uniform retardation $a$. First 24 cm: $\left(\frac{u}{3}\right)^2 = u^2 - 2a(24) \Rightarrow 2a(24) = \frac{8u^2}{9}$. Remaining distance $s$ to rest: $0 = \left(\frac{u}{3}\right)^2 - 2as \Rightarrow 2as = \frac{u^2}{9}$. Dividing: $\frac{s}{24} = \frac{1/9}{8/9} = \frac{1}{8} \Rightarrow s = 3$ cm. Total length $= 24 + 3 = 27$ cm. Check by energy: kinetic energy lost is $\frac{8}{9}$ of the whole in 24 cm, so the whole is lost in $24 \times \frac{9}{8} = 27$ cm. Answer: (1).
41	OpticsLenses and mirrors	Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics	Single correctHard
A hard single correct question on lenses and mirrors, from Optics. NCERT: Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics The figure shows a thin equiconvex lens of index $n_1 = 1.5$ ($R_1 = R_2 = 20$ cm) set in a slab of index $n_2 = 1.6$, which fills the space on either side. The combination is three thin lenses in contact: a plano-concave lens of $n_2$, the biconvex lens of $n_1$, and another plano-concave lens of $n_2$. Biconvex ($n_1 = 1.5$): $\frac{1}{f_1} = (1.5 - 1)\left(\frac{1}{20} + \frac{1}{20}\right) = \frac{1}{20}$. Each plano-concave ($n_2 = 1.6$): $\frac{1}{f_2} = (1.6 - 1)\left(-\frac{1}{20}\right) = -\frac{3}{100}$. $\frac{1}{F} = \frac{1}{20} - \frac{3}{100} - \frac{3}{100} = \frac{5 - 6}{100} = -\frac{1}{100}$, so $F = -100$ cm. Answer: (3) $-100$ cm.
42	Electronic DevicesLogic gates	Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits	Single correctEasy
A easy single correct question on logic gates, from Electronic Devices. NCERT: Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits Each input goes through a NOT gate, and the two inverted inputs feed a NAND gate: $Y = \overline{\bar{A}\cdot\bar{B}} = A + B$ (De Morgan), an OR gate. Truth table: $Y = 0$ only when $A = B = 0$; otherwise $Y = 1$: 00→0, 01→1, 10→1, 11→1. Answer: (2).
43	KinematicsMotion in a straight line	Class 11: Motion in a Straight Line; Class 11: Motion in a Plane	Single correctEasy
A easy single correct question on motion in a straight line, from Kinematics. NCERT: Class 11: Motion in a Straight Line; Class 11: Motion in a Plane Take upward positive, origin at the bridge: $s = ut - \frac{1}{2}gt^2 = 4(4) - \frac{1}{2}(10)(16) = 16 - 80 = -64$ m. The water is 64 m below the bridge. Check: the ball rises for 0.4 s to 0.8 m above the bridge, then falls 3.6 s: $\frac{1}{2}(10)(3.6)^2 = 64.8$ m, and $64.8 - 0.8 = 64$ m. Answer: (3).
44	Current ElectricityOhm's law	Class 12: Current Electricity	Single correctEasy
A easy single correct question on ohm's law, from Current Electricity. NCERT: Class 12: Current Electricity Series: $R_s = 10R$, $I_s = \frac{E}{10R}$. Parallel: $R_p = \frac{R}{10}$, $I_p = \frac{10E}{R}$. $n = \frac{I_p}{I_s} = \frac{10E/R}{E/10R} = 100$. Answer: (2).
45	Magnetic Effects of Current and MagnetismForce on moving charges and currents	Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter	Single correctEasy
A easy single correct question on force on moving charges and currents, from Magnetic Effects of Current and Magnetism. NCERT: Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter $\vec{F} = I\vec{L} \times \vec{B} = IL\,\hat{i} \times (2\hat{i} + 3\hat{j} - 4\hat{k}) = IL(0 + 3\hat{k} + 4\hat{j})$ (since $\hat{i}\times\hat{j} = \hat{k}$ and $\hat{i}\times\hat{k} = -\hat{j}$). $\|\vec{F}\| = IL\sqrt{3^2 + 4^2} = 5\,IL$. Only the components of $\vec{B}$ perpendicular to the wire count: $\sqrt{3^2 + 4^2} = 5$. Answer: (3).
46	GravitationOrbital motion	Class 11: Gravitation	Single correctMedium
A medium single correct question on orbital motion, from Gravitation. NCERT: Class 11: Gravitation For an orbit just above the surface (radius $R$): $T = 2\pi\sqrt{\frac{R^3}{GM}}$, with $M = \frac{4}{3}\pi R^3 d$. $T^2 = \frac{4\pi^2R^3}{G \cdot \frac{4}{3}\pi R^3 d} = \frac{3\pi}{Gd}$. Answer: (2) $T^2$.
47	Laws of MotionFriction	Class 11: Laws of Motion	Single correctEasy
A easy single correct question on friction, from Laws of Motion. NCERT: Class 11: Laws of Motion Static friction must supply the body's acceleration: $ma \le \mu_s mg$. $a_{max} = \mu_s g = 0.15 \times 10 = 1.5$ m s$^{-2}$. Answer: (3).
48	Current ElectricityResistivity	Class 12: Current Electricity	Single correctEasy
A easy single correct question on resistivity, from Current Electricity. NCERT: Class 12: Current Electricity $R_t = R_0(1 + \alpha t) \Rightarrow \alpha = \frac{R_t - R_0}{R_0 t} = \frac{6.8 - 2}{2 \times 80} = \frac{4.8}{160} = 0.03$ °C$^{-1}$ $= 3 \times 10^{-2}$ °C$^{-1}$. Answer: (3).
49	Atoms and NucleiBohr model	Class 12: Atoms; Class 12: Nuclei	Single correctEasy
A easy single correct question on bohr model, from Atoms and Nuclei. NCERT: Class 12: Atoms; Class 12: Nuclei Bohr radii grow as $n^2$: $r_n = n^2 r_1$. $r_3 = 9 \times 5.3 \times 10^{-11}$ m $= 4.77 \times 10^{-10}$ m $= 4.77$ Å. Answer: (4).
50	Magnetic Effects of Current and MagnetismBiot-Savart law	Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter	Single correctHard
A hard single correct question on biot-savart law, from Magnetic Effects of Current and Magnetism. NCERT: Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter P is the centre of the semicircle of radius $R$. The wire has three parts. Upper straight part (current to the right, ending at $A$ directly above P): a semi-infinite wire whose end is at the foot of the perpendicular from P, at distance $R$: $B_1 = \frac{\mu_0 i}{4\pi R}$. P is below a current flowing to the right, so $B_1$ is into the page. Lower straight part (current to the left, starting at $B$ directly below P): again $B_2 = \frac{\mu_0 i}{4\pi R}$; P is above a current flowing to the left, so $B_2$ is also into the page. Semicircle from $A$ (top) round the left to $B$ (bottom): the current goes anticlockwise as seen, so at its centre $B_3 = \frac{\mu_0 i}{4R}$ out of the page. Net (out of the page positive): $B = \frac{\mu_0 i}{4R} - 2\cdot\frac{\mu_0 i}{4\pi R} = \frac{\mu_0 i}{4R}\left[1 - \frac{2}{\pi}\right]$, out of the page since $1 > \frac{2}{\pi}$. Answer: (3).

Chemistry questions, each with its chapter and our explanation
Q	Chapter and topic	NCERT	Kind and level
51	AminesClassification and identification of amines	Class 12: Amines	Single correctEasy
A easy single correct question on classification and identification of amines, from Amines. NCERT: Class 12: Amines (1) Hofmann bromamide degradation: $\mathrm{CH_3CONH_2 + Br_2 + 4KOH \rightarrow CH_3NH_2}$ + …, a primary amine. (2) Reduction of a nitrile: $\mathrm{CH_3C{\equiv}N \rightarrow CH_3CH_2NH_2}$, a primary amine. (3) Reduction of an isocyanide: $\mathrm{CH_3N{\equiv}C \rightarrow CH_3NHCH_3}$ (N-methylmethanamine). The carbon of the isocyanide becomes a methyl group on nitrogen, so the product is a secondary amine. (4) Reduction of an amide: $\mathrm{CH_3CONH_2 \rightarrow CH_3CH_2NH_2}$, a primary amine. Answer: (3).
52	p-Block ElementsGroup 14 elements	No matching NCERT chapter	MatchingEasy
A easy matching question on group 14 elements, from p-Block Elements. NCERT: No matching NCERT chapter Coke (impure carbon) is used as a reducing agent in metallurgy: A-III. In diamond every carbon is $sp^3$ hybridised, bonded tetrahedrally to four others: B-I. Fullerenes ($\mathrm{C_{60}}$) are cage-like molecules: C-IV. Graphite's layers slide over each other, so it is used as a dry lubricant: D-II. Answer: (3) A-III, B-I, C-IV, D-II.
53	s-Block ElementsBiological importance of sodium, potassium, magnesium and calcium	No matching NCERT chapter	Assertion and reasonEasy
A easy assertion and reason question on biological importance of sodium, potassium, magnesium and calcium, from s-Block Elements. NCERT: No matching NCERT chapter A: alkali metals dissolve in liquid ammonia: $\mathrm{Na + (x+y)NH_3 \rightarrow [Na(NH_3)_x]^+ + [e(NH_3)_y]^-}$. The deep blue colour and the paramagnetism are due to the ammoniated (solvated) electrons, which are unpaired. A is true. R: the amide ($\mathrm{NaNH_2}$, with liberation of $\mathrm{H_2}$) forms only slowly, on standing, and it does not cause the blue colour. R is false. Answer: (3).
54	Organic Chemistry: Some Basic Principles and TechniquesQualitative and quantitative analysis	Class 11: Organic Chemistry – Some Basic Principles and Techniques	Single correctEasy
A easy single correct question on qualitative and quantitative analysis, from Organic Chemistry: Some Basic Principles and Techniques. NCERT: Class 11: Organic Chemistry – Some Basic Principles and Techniques When both N and S are present, fusion with sodium gives sodium thiocyanate, $\mathrm{Na + C + N + S \rightarrow NaSCN}$. With ferric ions it gives the blood-red complex: $\mathrm{Fe^{3+} + SCN^- \rightarrow [Fe(SCN)]^{2+}}$. ($\mathrm{Fe_4[Fe(CN)_6]_3}$, Prussian blue, is the test for N alone; $\mathrm{[Fe(CN)_5NOS]^{4-}}$, violet, is the nitroprusside test for S.) Answer: (4).
55	ElectrochemistryConductance	Class 12: Electrochemistry	Single correctEasy
A easy single correct question on conductance, from Electrochemistry. NCERT: Class 12: Electrochemistry Conductivity $\kappa = \frac{G^}{R}$, so the cell constant $G^ = \kappa R = 0.0210 \times 60 = 1.26$ cm$^{-1}$. Answer: (3).
56	Chemical KineticsArrhenius equation	Class 12: Chemical Kinetics	Assertion and reasonMedium
A medium assertion and reason question on arrhenius equation, from Chemical Kinetics. NCERT: Class 12: Chemical Kinetics R is the textbook definition of activation energy: the extra energy, over the average energy of the reactants, needed to reach the threshold energy. R is true. A: in the collision picture every reaction has an energy barrier, the threshold energy lying above the reactants' energy, so $E_a > 0$; if $E_a$ were zero, $k = Ae^{-E_a/RT}$ would equal $A$ and every collision would react whatever the temperature. In the sense of the syllabus A is false. Answer: (4).
57	Surface ChemistryPhysisorption and chemisorption	No matching NCERT chapter	Single correctEasy
A easy single correct question on physisorption and chemisorption, from Surface Chemistry. NCERT: No matching NCERT chapter Heterogeneous catalysis: the catalyst is in a different phase from the reactants. (1) $\mathrm{SO_2}$, $\mathrm{O_2}$ and NO are all gases: homogeneous. (2) Sugar and $\mathrm{H^+}$ both in solution: homogeneous. (3) $\mathrm{O_3}$ and NO both gases: homogeneous. (4) Haber process: gaseous $\mathrm{N_2}$ and $\mathrm{H_2}$ on solid iron — heterogeneous. Answer: (4).
58	Haloalkanes and HaloarenesNature of the C–X bond	Class 12: Haloalkanes and Haloarenes	Single correctEasy
A easy single correct question on nature of the c–x bond, from Haloalkanes and Haloarenes. NCERT: Class 12: Haloalkanes and Haloarenes The compound is $\mathrm{C_6H_5{-}CH{=}CH{-}CH(X){-}CH_2CH_3}$. The halogen is on an $sp^3$ carbon that is next to a C=C double bond (the carbon bearing X is attached to $\mathrm{CH{=}CH}$), so it is an allylic halide. It is not benzylic (X is not on the carbon attached to the ring), not aryl (X is not on the ring), and not vinylic (X is not on a doubly bonded carbon). Answer: (3).
59	AminesDiazonium salts	Class 12: Amines	Single correctEasy
A easy single correct question on diazonium salts, from Amines. NCERT: Class 12: Amines (i) Sandmeyer reaction: $\mathrm{C_6H_5N_2^+Cl^- \xrightarrow{Cu_2Br_2/HBr} C_6H_5Br + N_2}$. (ii) With Mg in dry ether, bromobenzene gives the Grignard reagent $\mathrm{C_6H_5MgBr}$. (iii) Water protonates the Grignard reagent: $\mathrm{C_6H_5MgBr + H_2O \rightarrow C_6H_6 + Mg(OH)Br}$. The product is benzene. Answer: (2).
60	p-Block ElementsGroup 17 and 18 elements	No matching NCERT chapter	Assertion and reasonEasy
A easy assertion and reason question on group 17 and 18 elements, from p-Block Elements. NCERT: No matching NCERT chapter A: helium is mixed with oxygen in the gas breathed by divers. True. R: the reason is helium's very low solubility in blood (unlike nitrogen, it does not dissolve under pressure and cause the bends). "High solubility in $\mathrm{O_2}$" is not the reason and is not true. R is false. Answer: (3).
61	Solid StateClose packed structures	No matching NCERT chapter	Single correctEasy
A easy single correct question on close packed structures, from Solid State. NCERT: No matching NCERT chapter In ccp there are 2 tetrahedral voids per atom. Take $N$ atoms of B: tetrahedral voids $= 2N$; A occupies $\frac{1}{3}(2N) = \frac{2N}{3}$. A : B $= \frac{2N}{3} : N = 2 : 3$, so the formula is $\mathrm{A_2B_3}$ and $x + y = 5$. Answer: (1).
62	BiomoleculesNucleic acids and vitamins	Class 12: Biomolecules	StatementsEasy
A easy statements question on nucleic acids and vitamins, from Biomolecules. NCERT: Class 12: Biomolecules Statement I: a base joined at the $1'$ carbon of the pentose sugar is a nucleoside. True. Statement II: a nucleoside esterified with phosphoric acid at the $5'$-OH of the sugar is a nucleotide. This is the textbook statement, printed here with "phosphorous acid" for phosphoric acid; read as intended, it is true. Answer: (1).
63	Structure of AtomQuantum numbers	Class 11: Structure of Atom	Single correctEasy
A easy single correct question on quantum numbers, from Structure of Atom. NCERT: Class 11: Structure of Atom For a given $l$, $m$ takes the values $-l, \ldots, 0, \ldots, +l$: $n_m = 2l + 1$. Rearranged: $l = \frac{n_m - 1}{2}$. Answer: (1).
64	Chemical Bonding and Molecular StructureVSEPR theory	Class 11: Chemical Bonding and Molecular Structure	Single correctEasy
A easy single correct question on vsepr theory, from Chemical Bonding and Molecular Structure. NCERT: Class 11: Chemical Bonding and Molecular Structure Count the electrons round the central atom: $\mathrm{NH_3}$: 3 bond pairs + 1 lone pair = 8. $\mathrm{AlCl_3}$: 3 bond pairs = 6 (incomplete octet). $\mathrm{BeCl_2}$: 2 bond pairs = 4 (incomplete octet). $\mathrm{CCl_4}$: 4 bond pairs = 8. $\mathrm{PCl_5}$: 5 bond pairs = 10 (expanded octet). Not eight: $\mathrm{AlCl_3}$, $\mathrm{BeCl_2}$, $\mathrm{PCl_5}$ — three. Answer: (1).
65	Chemical Bonding and Molecular StructureMolecular orbital theory	Class 11: Chemical Bonding and Molecular Structure	Single correctEasy
A easy single correct question on molecular orbital theory, from Chemical Bonding and Molecular Structure. NCERT: Class 11: Chemical Bonding and Molecular Structure For $\mathrm{N_2}$ (and lighter: $\mathrm{B_2}$, $\mathrm{C_2}$), 2s–2p mixing raises $\sigma 2p_z$ above the degenerate $\pi 2p_x, \pi 2p_y$ pair: $\sigma 1s < \sigma^* 1s < \sigma 2s < \sigma^* 2s < (\pi 2p_x = \pi 2p_y) < \sigma 2p_z < (\pi^* 2p_x = \pi^* 2p_y) < \sigma^* 2p_z$. (Option (2), with $\sigma 2p_z$ below the $\pi$ pair, is the order for $\mathrm{O_2}$ and $\mathrm{F_2}$.) Answer: (1).
66	Chemical Bonding and Molecular StructureHybridisation	Class 11: Chemical Bonding and Molecular Structure	Single correctEasy
A easy single correct question on hybridisation, from Chemical Bonding and Molecular Structure. NCERT: Class 11: Chemical Bonding and Molecular Structure Pyridine, $\mathrm{C_5H_5N}$: a six-membered ring of five C and one N with three alternating double bonds. σ bonds: 6 ring bonds + 5 C–H bonds = 11. π bonds: 3. Lone pairs: 1, on nitrogen (in an $sp^2$ orbital, outside the aromatic sextet). Answer: (3) 11, 3, 1.
67	Chemical Bonding and Molecular StructureHydrogen bonding	Class 11: Chemical Bonding and Molecular Structure	StatementsEasy
A easy statements question on hydrogen bonding, from Chemical Bonding and Molecular Structure. NCERT: Class 11: Chemical Bonding and Molecular Structure Intermolecular forces act between molecules: dispersion (London) forces, dipole–dipole forces, dipole–induced dipole forces, and hydrogen bonding (a strong dipole–dipole interaction). A covalent bond holds atoms together within a molecule; it is an intramolecular bond, not an intermolecular force. So D is excluded. Answer: (3) A, B, C, E.
68	HydrogenHydrogen and its compounds	No matching NCERT chapter	StatementsEasy
A easy statements question on hydrogen and its compounds, from Hydrogen. NCERT: No matching NCERT chapter A: hydrogen reduces heavy metal oxides to the metals. Correct. B: $\mathrm{D_2O}$ is used as a tracer to study reaction mechanisms. Correct. C: hydrogenation of vegetable oils gives saturated fats (vanaspati). Correct. D: the H–H bond dissociation enthalpy (435.88 kJ mol$^{-1}$) is the highest for a single bond between two atoms of any element, not the lowest. Not correct. E: hydrogen reduces oxides of metals less active than iron; it cannot reduce oxides of more active metals. Not correct. Answer: (3) D, E only.
69	PolymersNatural rubber and cellulose	No matching NCERT chapter	Single correctEasy
A easy single correct question on natural rubber and cellulose, from Polymers. NCERT: No matching NCERT chapter Neoprene is polychloroprene, made by free-radical polymerisation of chloroprene, 2-chlorobuta-1,3-diene: $\mathrm{CH_2{=}C(Cl){-}CH{=}CH_2}$. (1) buta-1,3-diene and (4) isoprene (which gives natural rubber) are other dienes; (3) is vinylacetylene, from which chloroprene is made. Answer: (2).
70	Chemistry in Everyday LifeDrugs and their classification	No matching NCERT chapter	Single correctEasy
A easy single correct question on drugs and their classification, from Chemistry in Everyday Life. NCERT: No matching NCERT chapter Barbiturates are derivatives of barbituric acid: veronal, amytal, nembutal, luminal and seconal are examples. Chlordiazepoxide and valium are benzodiazepines, and meprobamate is a carbamate tranquiliser. Answer: (4) Veronal.
71	Classification of Elements and PeriodicityPeriodic trends	Class 11: Classification of Elements and Periodicity in Properties	Single correctEasy
A easy single correct question on periodic trends, from Classification of Elements and Periodicity. NCERT: Class 11: Classification of Elements and Periodicity in Properties The ions are $\mathrm{N^{3-}}$, $\mathrm{O^{2-}}$, $\mathrm{F^-}$ and $\mathrm{Na^+}$, all isoelectronic with neon (10 electrons). For isoelectronic ions, the fewer the protons the larger the ion: N (7 protons) < O (8) < F (9) < Na (11). So $\mathrm{N^{3-}}$ is the largest. Answer: (3) N.
72	Structure of AtomBohr model	Class 11: Structure of Atom	StatementsEasy
A easy statements question on bohr model, from Structure of Atom. NCERT: Class 11: Structure of Atom A: atoms are made of three fundamental particles (electrons, protons and neutrons). Incorrect. B: $m_e = 9.10939 \times 10^{-31}$ kg. Correct. C: isotopes have the same number of electrons, so the same chemical properties. Correct. D: nucleons are protons and neutrons, the particles in the nucleus. Incorrect. E: Dalton regarded the atom as the ultimate, indivisible particle of matter. Correct. Answer: (4) B, C and E only.
73	Haloalkanes and HaloarenesSN1 and SN2 mechanisms	Class 12: Haloalkanes and Haloarenes	Single correctMedium
A medium single correct question on sn1 and sn2 mechanisms, from Haloalkanes and Haloarenes. NCERT: Class 12: Haloalkanes and Haloarenes The secondary alcohol reacts with HBr by the $S_N1$ path: protonation of OH and loss of water give the secondary carbocation $\mathrm{(CH_3)_2CH{-}\overset{+}{C}H{-}CH_3}$. A 1,2-hydride shift from the neighbouring carbon gives the more stable tertiary carbocation $\mathrm{(CH_3)_2\overset{+}{C}{-}CH_2CH_3}$. $\mathrm{Br^-}$ attacks it: $\mathrm{CH_3{-}C(Br)(CH_3){-}CH_2{-}CH_3}$, 2-bromo-2-methylbutane. Answer: (1).
74	d- and f-Block ElementsTransition element properties	Class 12: The d- and f-Block Elements	Single correctEasy
A easy single correct question on transition element properties, from d- and f-Block Elements. NCERT: Class 12: The d- and f-Block Elements $\mathrm{Cu^+}$ ($3d^{10}$) has the more stable configuration, and forming $\mathrm{Cu^{2+}}$ costs the second ionisation enthalpy. In water, however, the much more negative hydration enthalpy of the small, doubly charged $\mathrm{Cu^{2+}}$ more than makes up for it, so $\mathrm{Cu^{2+}(aq)}$ is more stable and $\mathrm{Cu^+}$ disproportionates: $\mathrm{2Cu^+ \rightarrow Cu^{2+} + Cu}$. Answer: (3).
75	s-Block ElementsBiological importance of sodium, potassium, magnesium and calcium	No matching NCERT chapter	Single correctMedium
A medium single correct question on biological importance of sodium, potassium, magnesium and calcium, from s-Block Elements. NCERT: No matching NCERT chapter (1) The daily requirement of magnesium and calcium in the human body is estimated at 200–300 mg, i.e. 0.2–0.3 g. Correct. (2) The enzymes that use ATP in phosphate transfer need magnesium, not calcium, as the cofactor. Incorrect. (3) Bone is not inert: it is continually dissolved and redeposited (about 400 mg of calcium a day in an adult). Incorrect. (4) It is calcium that has the roles in neuromuscular function, interneuronal transmission, cell membrane integrity and blood coagulation. Incorrect. Answer: (1).
76	HydrocarbonsAlkanes	Class 11: Hydrocarbons	Single correctEasy
A easy single correct question on alkanes, from Hydrocarbons. NCERT: Class 11: Hydrocarbons Decarboxylation with soda lime: $\mathrm{CH_3COONa + NaOH \xrightarrow{CaO,\ \Delta} CH_4 + Na_2CO_3}$. Methane, $M = 16$ g mol$^{-1}$; two moles weigh 32 g. Answer: (2).
77	EquilibriumIonic equilibrium	Class 11: Equilibrium	Single correctEasy
A easy single correct question on ionic equilibrium, from Equilibrium. NCERT: Class 11: Equilibrium A Lewis acid accepts an electron pair. In $\mathrm{BF_3}$ boron has only six electrons and a vacant orbital, so it accepts a pair (e.g. $\mathrm{BF_3 + NH_3 \rightarrow F_3B{\leftarrow}NH_3}$). $\mathrm{NH_3}$, $\mathrm{H_2O}$ and $\mathrm{OH^-}$ have lone pairs to donate: they are Lewis bases. Answer: (3).
78	Aldehydes, Ketones and Carboxylic AcidsNucleophilic addition	Class 12: Aldehydes, Ketones and Carboxylic Acids	Single correctEasy
A easy single correct question on nucleophilic addition, from Aldehydes, Ketones and Carboxylic Acids. NCERT: Class 12: Aldehydes, Ketones and Carboxylic Acids Zn–Hg with concentrated HCl is the Clemmensen reduction: it reduces a ketone C=O to $\mathrm{CH_2}$ ($\mathrm{>C{=}O \rightarrow >CH_2 + H_2O}$). The starting compound has two acetyl groups (one on the cyclohexane ring, one on the benzene ring); both are reduced, each $\mathrm{{-}COCH_3}$ becoming $\mathrm{{-}CH_2CH_3}$, which also accounts for the $\mathrm{2H_2O}$ in the equation. (A) is the compound with two ethyl groups: option (1). Option (2) shows reduction only to the secondary alcohols (that is what $\mathrm{NaBH_4}$ would give); (3) keeps oxygen and (4) has lost a carbon from each side chain. Answer: (1).
79	p-Block ElementsGroup 13 elements	No matching NCERT chapter	Single correctMedium
A medium single correct question on group 13 elements, from p-Block Elements. NCERT: No matching NCERT chapter Down group 13 the inert pair effect makes the +1 state more stable and the +3 state less stable. (1) For thallium +1 is the more stable state, so $\mathrm{TlCl > TlCl_3}$: (1) is wrong. (3) For aluminium +3 is far the more stable state, so $\mathrm{AlCl_3 > AlCl}$: (3) is wrong. (4) For thallium $\mathrm{TlI > TlI_3}$ (indeed "$\mathrm{TlI_3}$" is really $\mathrm{Tl^+(I_3^-)}$, a thallium(I) compound): correct. (2) For indium the +3 state is still the more stable, so $\mathrm{InI_3 > InI}$ is also true as written. The question targets the inert pair effect of thallium; taking (4) as the intended answer. Answer: (4).
80	Coordination CompoundsNomenclature	Class 12: Coordination Compounds	Single correctEasy
A easy single correct question on nomenclature, from Coordination Compounds. NCERT: Class 12: Coordination Compounds A homoleptic complex has only one kind of ligand round the metal. (1) $\mathrm{K_3[Al(C_2O_4)_3]}$: only oxalate ligands — homoleptic. (2) $\mathrm{[Pt(NH_3)_2Cl(NO_2)]}$, (3) $\mathrm{[Co(NH_3)_5(CO_3)]Cl}$ and (4) $\mathrm{[Cr(NH_3)_3(H_2O)_3]Cl_3}$ each have two or more kinds: heteroleptic. Answer: (1).
81	Aldehydes, Ketones and Carboxylic AcidsNucleophilic addition	Class 12: Aldehydes, Ketones and Carboxylic Acids	Single correctMedium
A medium single correct question on nucleophilic addition, from Aldehydes, Ketones and Carboxylic Acids. NCERT: Class 12: Aldehydes, Ketones and Carboxylic Acids [A] cyclohexanone adds HCN to give the cyanohydrin [B], 1-hydroxycyclohexane-1-carbonitrile. Hot concentrated $\mathrm{H_2SO_4}$ hydrolyses the nitrile, $\mathrm{{-}CN \rightarrow {-}COOH}$, and dehydrates the tertiary alcohol, removing OH and a ring hydrogen to put the double bond in the ring next to the carboxyl group (conjugated with it). [C] is cyclohex-1-ene-1-carboxylic acid. Answer: (4).
82	States of MatterGas laws	No matching NCERT chapter	Single correctEasy
A easy single correct question on gas laws, from States of Matter. NCERT: No matching NCERT chapter Boyle's law: at constant temperature $PV = nRT$ = constant, so $P = nRT \cdot \frac{1}{V}$. A plot of $P$ against $\frac{1}{V}$ is a straight line through the origin with slope $nRT$: the higher the temperature, the steeper the line. Graph (2) shows straight lines with the steepest for $T_3$, the highest temperature: correct. (1) $P$–$V$ hyperbolas, but with $T_1$, the lowest temperature, drawn farthest from the axes; the highest temperature should be farthest. Wrong. (3) $P$ against $\frac{1}{V}$ drawn as hyperbolas. Wrong shape. (4) $P$ against $T$ at constant volume is Gay-Lussac's (pressure–temperature) law, not Boyle's law. Answer: (2).
83	Some Basic Concepts of ChemistryStoichiometry	Class 11: Some Basic Concepts of Chemistry	Single correctEasy
A easy single correct question on stoichiometry, from Some Basic Concepts of Chemistry. NCERT: Class 11: Some Basic Concepts of Chemistry Pure $\mathrm{CaCO_3}$ $= 20\% \times 20$ g $= 4$ g. $M(\mathrm{CaCO_3}) = 40 + 12 + 48 = 100$ g mol$^{-1}$, so 0.04 mol. One mole of $\mathrm{CaCO_3}$ gives one mole of $\mathrm{CO_2}$ (44 g mol$^{-1}$): $0.04 \times 44 = 1.76$ g. Check: $\frac{44}{100} \times 4 = 1.76$ g. Answer: (2).
84	Chemical KineticsRate laws	Class 12: Chemical Kinetics	Single correctEasy
A easy single correct question on rate laws, from Chemical Kinetics. NCERT: Class 12: Chemical Kinetics Rate $\propto [A]^2$ at constant [B]. Tripling [A]: new rate $= k(3[A])^2[B] = 9k[A]^2[B]$. The rate increases by a factor of nine. Answer: (3).
85	ElectrochemistryElectrochemical cells	Class 12: Electrochemistry	Assertion and reasonMedium
A medium assertion and reason question on electrochemical cells, from Electrochemistry. NCERT: Class 12: Electrochemistry A: $\Delta_rG = -nFE_{cell}$; for the same cell written for twice the amount of reaction, $n$ doubles and so does $\Delta_rG$. True. R: $E_{cell}$ does not depend on the amount of substance (intensive), whereas $\Delta_rG$ does (extensive). True. Because $E_{cell}$ is intensive while $\Delta_rG$ is extensive, the relation has to carry $n$, the amount of electrons transferred, to scale $\Delta_rG$ with the amount of reaction. R is the reason for A. Answer: (1).
86	p-Block ElementsGroup 16 elements	No matching NCERT chapter	MatchingEasy
A easy matching question on group 16 elements, from p-Block Elements. NCERT: No matching NCERT chapter Peroxodisulphuric acid $\mathrm{H_2S_2O_8}$: $\mathrm{HO{-}S(O_2){-}O{-}O{-}S(O_2){-}OH}$ — two S–OH, four S=O, one S–O–O–S: A-III. Sulphuric acid $\mathrm{H_2SO_4}$: $\mathrm{(HO)_2SO_2}$ — two S–OH, two S=O: B-IV. Pyrosulphuric acid $\mathrm{H_2S_2O_7}$: $\mathrm{HO{-}S(O_2){-}O{-}S(O_2){-}OH}$ — two S–OH, four S=O, one S–O–S: C-I. Sulphurous acid $\mathrm{H_2SO_3}$: $\mathrm{(HO)_2S{=}O}$ — two S–OH, one S=O: D-II. Answer: (2) A-III, B-IV, C-I, D-II.
87	d- and f-Block ElementsTransition element properties	Class 12: The d- and f-Block Elements	StatementsMedium
A medium statements question on transition element properties, from d- and f-Block Elements. NCERT: Class 12: The d- and f-Block Elements A: all the first-series metals except scandium form ionic oxides MO. Correct. B: from $\mathrm{Sc_2O_3}$ to $\mathrm{Mn_2O_7}$ the oxides reach the group oxidation number (+3 … +7). Correct. C: as the oxidation state rises the oxides become less basic and more acidic: $\mathrm{V_2O_3}$ basic, $\mathrm{V_2O_4}$ less basic, $\mathrm{V_2O_5}$ amphoteric (mainly acidic). Basic character decreases, so C is INCORRECT. D: $\mathrm{V_2O_4}$ dissolves in acids to give $\mathrm{VO^{2+}}$ (vanadyl) salts; $\mathrm{VO_4^{3-}}$ comes from $\mathrm{V_2O_5}$ in alkali. INCORRECT. E: CrO is basic and $\mathrm{Cr_2O_3}$ amphoteric. Correct. Answer: (3) C and D only.
88	Coordination CompoundsCrystal field theory	Class 12: Coordination Compounds	Single correctMedium
A medium single correct question on crystal field theory, from Coordination Compounds. NCERT: Class 12: Coordination Compounds All four are cobalt(III) complexes. Only (3) contains a chelating ligand: each ethane-1,2-diamine (en) binds through both nitrogens and forms a five-membered ring with the metal. Chelation (the chelate effect) makes a complex markedly more stable than one with comparable monodentate ligands such as $\mathrm{NH_3}$, $\mathrm{H_2O}$, $\mathrm{Br^-}$ or $\mathrm{NO_3^-}$. So $\mathrm{[CoCl_2(en)_2]NO_3}$ is the most stable. Answer: (3).
89	HydrocarbonsAromatic hydrocarbons	Class 11: Hydrocarbons	Single correctMedium
A medium single correct question on aromatic hydrocarbons, from Hydrocarbons. NCERT: Class 11: Hydrocarbons Hückel's rule: a planar, cyclic, fully conjugated system with $(4n + 2)$ π electrons is aromatic. i. Naphthalene: 10 π electrons ($n = 2$). Obeys. ii. Cyclopentadienyl anion: 4 π electrons + the lone pair = 6 ($n = 1$). Obeys. iii. Cyclobutadiene: 4 π electrons ($4n$). Does not. iv. Cyclopropenyl anion: 2 π electrons + the lone pair = 4 ($4n$). Does not. v. Cyclopropenyl cation: 2 π electrons ($n = 0$). Obeys. vi. Cyclooctatetraene: 8 π electrons, and the ring is tub-shaped, not planar. Does not. vii. Anthracene: 14 π electrons ($n = 3$). Obeys. Four species: i, ii, v and vii. Answer: (1) 4.
90	Solid StatePacking in fcc, bcc and hcp	No matching NCERT chapter	Single correctEasy
A easy single correct question on packing in fcc, bcc and hcp, from Solid State. NCERT: No matching NCERT chapter An octahedral void at the centre of a cube edge is shared by the four unit cells that meet at that edge. So $\frac{1}{4}$ of it lies in one unit cell (12 edges × $\frac{1}{4}$ = 3, plus the body-centre void, gives the 4 octahedral voids of an fcc cell). Answer: (3).
91	ThermodynamicsFirst law and state functions	Class 11: Thermodynamics	Single correctEasy
A easy single correct question on first law and state functions, from Thermodynamics. NCERT: Class 11: Thermodynamics $H = U + PV$, so at constant temperature and pressure $\Delta H = \Delta U + P\Delta V$. For ideal gases $P\Delta V = \Delta n_g RT$, where $\Delta n_g$ is the change in moles of gas. $\Delta H = \Delta U + \Delta n_g RT$. Answer: (2).
92	Redox ReactionsBalancing redox equations	Class 11: Redox Reactions	Single correctEasy
A easy single correct question on balancing redox equations, from Redox Reactions. NCERT: Class 11: Redox Reactions Electrons: each Cr goes +6 → +3, so one $\mathrm{Cr_2O_7^{2-}}$ takes 6 electrons; each S goes +4 → +6, giving 2 electrons. So $a = 1$, $b = 3$. Charge: left $-2 - 6 + c$, right $2(+3) - 6 = 0$, so $c - 8 = 0$, $c = 8$. $\mathrm{Cr_2O_7^{2-} + 3SO_3^{2-} + 8H^+ \rightarrow 2Cr^{3+} + 3SO_4^{2-} + 4H_2O}$. Oxygen check: left $7 + 9 = 16$, right $12 + 4 = 16$. Hydrogen: 8 = 2 × 4. Answer: (1) 1, 3, 8.
93	ThermodynamicsEntropy and Gibbs energy	Class 11: Thermodynamics	Single correctEasy
A easy single correct question on entropy and gibbs energy, from Thermodynamics. NCERT: Class 11: Thermodynamics $K = \frac{[C][D]}{[A][B]} = \frac{10 \times 6}{2 \times 3} = 10$. $\Delta G° = -2.303RT\log K = -2.303 \times 2 \times 300 \times \log 10 = -1381.8$ cal. Answer: (3).
94	Surface ChemistryColloids and their preparation	No matching NCERT chapter	Single correctEasy
A easy single correct question on colloids and their preparation, from Surface Chemistry. NCERT: No matching NCERT chapter Pumice stone is a colloid of a gas (dispersed phase) in a solid (dispersion medium). That type of colloid is called a solid sol (examples: pumice stone, foam rubber). A "foam" is gas in a liquid, a "gel" is liquid in a solid, and a "sol" is solid in a liquid. Answer: (3).
95	Aldehydes, Ketones and Carboxylic AcidsTests to distinguish aldehydes and ketones	Class 12: Aldehydes, Ketones and Carboxylic Acids	Single correctMedium
A medium single correct question on tests to distinguish aldehydes and ketones, from Aldehydes, Ketones and Carboxylic Acids. NCERT: Class 12: Aldehydes, Ketones and Carboxylic Acids The reactant is 2-acetylbenzaldehyde, which has an aldehyde group and a ketone group. Tollens' reagent, $\mathrm{[Ag(NH_3)_2]^+}$ in alkali, is a mild oxidant: it oxidises the aldehyde ($\mathrm{{-}CHO \rightarrow {-}COO^-}$, depositing silver) and leaves the ketone untouched; nothing reduces either group. Major product: 2-acetylbenzoate, the ring carrying $\mathrm{{-}COCH_3}$ and $\mathrm{{-}COO^-}$. Answer: (3).
96	Haloalkanes and HaloarenesNature of the C–X bond	Class 12: Haloalkanes and Haloarenes	Single correctMedium
A medium single correct question on nature of the c–x bond, from Haloalkanes and Haloarenes. NCERT: Class 12: Haloalkanes and Haloarenes $\mathrm{CH_3CHO \xrightarrow{LiAlH_4,\ H_3O^+} CH_3CH_2OH}$ [A] (reduction). $\mathrm{CH_3CH_2OH \xrightarrow{H_2SO_4,\ \Delta} CH_2{=}CH_2}$ [B] (dehydration). $\mathrm{CH_2{=}CH_2 \xrightarrow{HBr} CH_3CH_2Br}$ [C]. With bromobenzene and sodium in dry ether (Wurtz–Fittig reaction): $\mathrm{C_6H_5Br + CH_3CH_2Br + 2Na \rightarrow C_6H_5CH_2CH_3 + 2NaBr}$. [D] is ethylbenzene. Answer: (1).
97	Alcohols, Phenols and EthersPreparation and properties	Class 12: Alcohols, Phenols and Ethers	Single correctHard
A hard single correct question on preparation and properties, from Alcohols, Phenols and Ethers. NCERT: Class 12: Alcohols, Phenols and Ethers Look at what dehydration gives in each case. (3) 3-Nitrobutane-1,2-diol has its secondary OH on the carbon next to the carbon carrying $\mathrm{NO_2}$, and that carbon carries a hydrogen. A hydrogen $\alpha$ to a nitro group is strongly acidic, so it is lost very easily, and losing it with the neighbouring OH gives an alkene conjugated with the nitro group, $\mathrm{CH_3{-}C(NO_2){=}CH{-}CH_2OH}$. β-Nitro alcohols are dehydrated very readily for exactly this reason. In (1) 4-nitropentan-2-ol and (4) 5-nitrohexan-2-ol the OH is too far from the nitro group for its α-hydrogen to take part, and the alkene formed is not conjugated with $\mathrm{NO_2}$; in (2) pentane-2,4-diol there is no such activating group at all. These need an ordinary secondary carbocation and dehydrate less readily. Answer: (3).
98	Environmental ChemistryAir and water pollution	No matching NCERT chapter	StatementsEasy
A easy statements question on air and water pollution, from Environmental Chemistry. NCERT: No matching NCERT chapter Statement I: eutrophication is caused by nutrient enrichment (phosphates and nitrates) of water bodies, not by nutrient deficiency. Incorrect. Statement II: the dense algal growth that follows, and its decay by bacteria, use up the dissolved oxygen, so the oxygen level falls. True. Answer: (4).
99	Alcohols, Phenols and EthersWilliamson synthesis	Class 12: Alcohols, Phenols and Ethers	Single correctMedium
A medium single correct question on williamson synthesis, from Alcohols, Phenols and Ethers. NCERT: Class 12: Alcohols, Phenols and Ethers Benzyl phenyl ether, $\mathrm{C_6H_5CH_2{-}O{-}C_6H_5}$, is cleaved by hot HI. The ether oxygen is protonated; iodide then attacks the benzylic carbon (the benzyl cation is stabilised, and an aryl carbon cannot be attacked because the $\mathrm{O{-}C_{aryl}}$ bond has partial double-bond character). $\mathrm{C_6H_5CH_2{-}O{-}C_6H_5 + HI \rightarrow C_6H_5CH_2I + C_6H_5OH}$. A = benzyl iodide, B = phenol. Answer: (3).
100	Isolation of MetalsSmelting and refining	No matching NCERT chapter	Single correctMedium
A medium single correct question on smelting and refining, from Isolation of Metals. NCERT: No matching NCERT chapter In the blast furnace, the upper, cooler zone (500–800 K) is where $\mathrm{Fe_2O_3}$ is reduced by CO: $\mathrm{3Fe_2O_3 + CO \rightarrow 2Fe_3O_4 + CO_2}$, $\mathrm{Fe_3O_4 + 4CO \rightarrow 3Fe + 4CO_2}$, $\mathrm{Fe_2O_3 + CO \rightarrow 2FeO + CO_2}$. In the hotter zone (900–1500 K): $\mathrm{C + CO_2 \rightarrow 2CO}$ and $\mathrm{FeO + CO \rightarrow Fe + CO_2}$; limestone decomposes to CaO, which combines with silica as slag, $\mathrm{CaO + SiO_2 \rightarrow CaSiO_3}$. So the reduction of $\mathrm{Fe_2O_3}$ to FeO is the one that does not belong to 900–1500 K. Answer: (1).

Botany questions, each with its chapter and our explanation
Q	Chapter and topic	NCERT	Kind and level
101	Plant KingdomBryophytes and pteridophytes	Class 11: Plant Kingdom	Assertion and reasonEasy
A easy assertion and reason question on bryophytes and pteridophytes, from Plant Kingdom. NCERT: Class 11: Plant Kingdom In a moss the spores are formed by meiosis in the capsule of the sporophyte. On release, a spore germinates directly into the protonema: a creeping, green, branched and often filamentous stage. It is the first stage of the gametophyte. The second stage, the leafy stage, grows later from lateral buds on the protonema. So A is correct. R is also correct, and it is the reason A holds: because the protonema is what the spore itself grows into, it must be the first stage of the gametophyte. Answer: (1).
102	Sexual Reproduction in Flowering PlantsDouble fertilisation	Class 12: Sexual Reproduction in Flowering Plants	Single correctEasy
A easy single correct question on double fertilisation, from Sexual Reproduction in Flowering Plants. NCERT: Class 12: Sexual Reproduction in Flowering Plants After double fertilisation the embryo sac holds: - the synergids and antipodals, cells of the female gametophyte, so haploid (n); - the zygote, egg (n) + one male gamete (n), so diploid (2n); - the primary endosperm nucleus, two polar nuclei (n + n) + the second male gamete (n), so triploid (3n). In the required order haploid, diploid, triploid: synergids, zygote, primary endosperm nucleus. Option (1) has the PEN and zygote in the wrong order; (2) gives synergids (haploid) as the diploid structure; (4) has no diploid or triploid structure, since the polar nuclei are each haploid. Answer: (3).
103	Cell: The Unit of LifeCell membrane	Class 11: Cell: The Unit of Life	Single correctEasy
A easy single correct question on cell membrane, from Cell: The Unit of Life. NCERT: Class 11: Cell: The Unit of Life Diffusion, facilitated diffusion and osmosis all move substances down a gradient (from higher to lower concentration or water potential) and need no energy: they are passive transport. Moving ions against their concentration gradient, so that they accumulate on one side of the membrane, needs energy from ATP and carrier proteins (pumps, such as the Na$^+$/K$^+$ pump). This is active transport. Answer: (4).
104	Sexual Reproduction in Flowering PlantsPollination and outbreeding devices	Class 12: Sexual Reproduction in Flowering Plants	Single correctEasy
A easy single correct question on pollination and outbreeding devices, from Sexual Reproduction in Flowering Plants. NCERT: Class 12: Sexual Reproduction in Flowering Plants Insects such as bees, butterflies and moths find flowers by colour and scent and feed on nectar and pollen. Insect-pollinated flowers are therefore generally large, colourful, fragrant and rich in nectar; small ones are clustered into an inflorescence to be conspicuous. Wind-pollinated flowers are small, dull, without scent or nectar. Birds have little sense of smell, so bird flowers are rarely fragrant; bat flowers open at night and are usually dull-coloured. Answer: (1).
105	Principles of Inheritance and VariationDeviations from Mendelism	Class 12: Principles of Inheritance and Variation	Single correctEasy
A easy single correct question on deviations from mendelism, from Principles of Inheritance and Variation. NCERT: Class 12: Principles of Inheritance and Variation Pleiotropy is the case where a single gene has more than one phenotypic effect. In phenylketonuria, for example, a mutation in the single gene for phenylalanine hydroxylase causes mental retardation and also reduced hair and skin pigmentation. Several alleles of one gene describe multiple allelism; several genes controlling one character is polygenic inheritance (option 4). Answer: (3).
106	Plant Growth and DevelopmentPlant hormones	Class 11: Plant Growth and Development	Single correctEasy
A easy single correct question on plant hormones, from Plant Growth and Development. NCERT: Class 11: Plant Growth and Development Ethylene, a gaseous hormone, promotes rapid internode and petiole elongation in deep water rice plants. This keeps the leaves and upper parts of the shoot above the water as the water level rises. Gibberellins also lengthen internodes in many plants, but the response in deep water rice is the textbook example of ethylene action. Kinetin is a cytokinin (cell division, delay of senescence) and 2,4-D is a synthetic auxin used as a weedicide. Answer: (3).
107	Biodiversity and ConservationPatterns of biodiversity	Class 12: Biodiversity and Conservation	Single correctEasy
A easy single correct question on patterns of biodiversity, from Biodiversity and Conservation. NCERT: Class 12: Biodiversity and Conservation The four major causes of biodiversity loss, 'the Evil Quartet', are habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions. Of these, habitat loss and fragmentation is the most important cause of the extinction of plants and animals: tropical rain forests, which once covered 14 per cent of the land surface, now cover no more than 6 per cent, and when large habitats are broken into fragments the animals that need large territories decline. Answer: (1).
109	Mineral NutritionEssential elements and their functions	No matching NCERT chapter	Single correctEasy
A easy single correct question on essential elements and their functions, from Mineral Nutrition. NCERT: No matching NCERT chapter Manganese activates many enzymes of photosynthesis, respiration and nitrogen metabolism; its best defined function is in the splitting of water to liberate oxygen during photosynthesis (it is part of the water-splitting complex of PS II). Magnesium is a macronutrient, present at the centre of the chlorophyll molecule. Molybdenum is a component of nitrogenase and nitrate reductase. Copper takes part in redox reactions (plastocyanin) but does not split water. Answer: (1).
110	Morphology of Flowering PlantsFlower and fruit	Class 11: Morphology of Flowering Plants	Single correctMedium
A medium single correct question on flower and fruit, from Morphology of Flowering Plants. NCERT: Class 11: Morphology of Flowering Plants In axile placentation the placenta is axial and the ovules are attached to it in a multilocular ovary, as in china rose, tomato, lemon and Petunia (Solanaceae has a bilocular ovary with a swollen axile placenta). Check the others: mustard is parietal, cucumber parietal, primrose free central; beans, lupin and pea are marginal (Fabaceae); Dianthus is free central. Only option (4) has all three axile. Answer: (4).
111	Cell Cycle and Cell DivisionMeiosis	Class 11: Cell Cycle and Cell Division	Single correctEasy
A easy single correct question on meiosis, from Cell Cycle and Cell Division. NCERT: Class 11: Cell Cycle and Cell Division In zygotene homologous chromosomes pair (synapsis) and the synaptonemal complex forms. In pachytene the bivalents are clearly seen as tetrads, and recombination nodules appear: they are the sites at which crossing over occurs between non-sister chromatids of homologous chromosomes. In diplotene the synaptonemal complex dissolves and chiasmata become visible; in diakinesis the chiasmata terminalise. Answer: (2).
112	Photosynthesis in Higher PlantsLight reaction	Class 11: Photosynthesis in Higher Plants	Single correctEasy
A easy single correct question on light reaction, from Photosynthesis in Higher Plants. NCERT: Class 11: Photosynthesis in Higher Plants Each photosystem has a reaction centre chlorophyll a named for its absorption peak. The reaction centre of PS I is P700 (absorbs best at 700 nm); that of PS II is P680 (680 nm). Answer: (1).
113	Molecular Basis of InheritanceDNA structure	Class 12: Molecular Basis of Inheritance	Single correctEasy
A easy single correct question on dna structure, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance Griffith (1928) showed only that some 'transforming principle' passed from heat-killed S strain to R strain pneumococcus. Avery, MacLeod and McCarty (1933–44) showed the principle was DNA, but not all biologists were convinced. The unequivocal proof came from Hershey and Chase (1952): bacteriophages grown with radioactive $^{32}$P (labelling DNA) passed the label into the bacteria, while those grown with $^{35}$S (labelling protein) did not. So DNA, not protein, is what enters and carries the genetic information. Wilkins and Franklin produced the X-ray diffraction data for DNA's structure. Answer: (2).
114	Cell Cycle and Cell DivisionMitosis	Class 11: Cell Cycle and Cell Division	Single correctEasy
A easy single correct question on mitosis, from Cell Cycle and Cell Division. NCERT: Class 11: Cell Cycle and Cell Division Interphase has three phases: G$_1$ (the cell grows but does not copy its DNA), S or synthesis phase (DNA replication: the amount of DNA per cell doubles, from 2C to 4C) and G$_2$ (proteins are made in preparation for mitosis). The M phase is the division itself. So DNA replicates in the S phase. Answer: (2).
115	Plant Growth and DevelopmentSeed germination and differentiation	Class 11: Plant Growth and Development	Single correctEasy
A easy single correct question on seed germination and differentiation, from Plant Growth and Development. NCERT: Class 11: Plant Growth and Development Mesophyll cells are differentiated: they have lost the ability to divide. When such cells regain the capacity to divide under certain conditions, the process is dedifferentiation. In tissue culture the mesophyll cells divide again to form a mass of undifferentiated cells, the callus, so this is dedifferentiation. Cells of the callus later redifferentiate into shoots and roots. Answer: (2).
117	Plant Growth and DevelopmentPlant hormones	Class 11: Plant Growth and Development	Single correctEasy
A easy single correct question on plant hormones, from Plant Growth and Development. NCERT: Class 11: Plant Growth and Development Gibberellins hasten the maturity period of juvenile conifers when sprayed on them, which leads to early seed production. They also elongate the stems of sugarcane, delay senescence of fruits and promote bolting. IBA is an auxin (rooting of cuttings), zeatin a cytokinin, and abscisic acid a growth inhibitor that promotes dormancy. Answer: (2).
118	Transport in PlantsWater movement in plants	No matching NCERT chapter	StatementsMedium
A medium statements question on water movement in plants, from Transport in Plants. NCERT: No matching NCERT chapter Statement I: by the cohesion–tension–transpiration pull model, the forces generated by transpiration can create pressures sufficient to lift a xylem-sized column of water over 130 metres high. Correct. Statement II: among the purposes of transpiration, it cools leaf surfaces, sometimes 10 to 15 degrees, by evaporative cooling. Correct. Both statements are correct. Answer: (1).
119	Morphology of Flowering PlantsPlant families: Malvaceae, Cruciferae, Leguminosae, Compositae, Gramineae	Class 11: Morphology of Flowering Plants	Single correctMedium
A medium single correct question on plant families: malvaceae, cruciferae, leguminosae, compositae, gramineae, from Morphology of Flowering Plants. NCERT: Class 11: Morphology of Flowering Plants Fabaceae: ten stamens, diadelphous (9 + 1), anthers dithecous. Solanaceae: five stamens, epipetalous (fused to the petals), free. Liliaceae: six stamens in two whorls of three, epiphyllous (fused to the perianth). Diadelphous stamens are found only in Fabaceae, so option (1) is the feature specific to it. Epipetalous belongs to Solanaceae and epiphyllous to Liliaceae; monadelphous stamens are typical of Malvaceae. Answer: (1).
120	Molecular Basis of InheritanceHuman genome project	Class 12: Molecular Basis of Inheritance	Single correctEasy
A easy single correct question on human genome project, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance The Human Genome Project used two approaches. One, Expressed Sequence Tags (ESTs), focused on identifying all the genes that are expressed as RNA. The other, sequence annotation, sequenced the whole set of the genome, coding and non-coding, and later assigned functions to regions. Answer: (1).
121	EcosystemProductivity and decomposition	Class 12: Ecosystem	StatementsMedium
A medium statements question on productivity and decomposition, from Ecosystem. NCERT: Class 12: Ecosystem A. Correct. Detritivores such as the earthworm break detritus into smaller particles: fragmentation. B. Correct. Humus is highly resistant to microbial action and decomposes very slowly; it is further degraded by some microbes, and nutrients are released by mineralisation. C. Correct. In leaching, water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. D. Incorrect. The detritus food chain begins with dead organic matter; it is the grazing food chain that begins with living producers. E. Incorrect. The breakdown by earthworms into smaller particles is fragmentation; catabolism is the enzymatic breakdown of detritus by bacteria and fungi into simpler inorganic substances. So A, B and C only. Answer: (1).
122	Environmental IssuesOzone depletion	No matching NCERT chapter	Single correctEasy
A easy single correct question on ozone depletion, from Environmental Issues. NCERT: No matching NCERT chapter The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in Dobson units (DU). Decibels measure sound intensity, decametre is a length, and a kilobase is 1000 base pairs of nucleic acid. Answer: (1).
123	Anatomy of Flowering PlantsAnatomy of root, stem and leaf	Class 11: Anatomy of Flowering Plants	Assertion and reasonMedium
A medium assertion and reason question on anatomy of root, stem and leaf, from Anatomy of Flowering Plants. NCERT: Class 11: Anatomy of Flowering Plants The activity of the vascular cambium varies with the season. In spring it is very active and produces many xylary elements with wide vessels: spring wood or early wood. In winter it is less active and forms fewer xylary elements with narrow vessels: autumn wood or late wood. A is true; R is true; and late wood is like this precisely because the cambium is less active in the cold season. So R explains A. Answer: (1).
124	Cell Cycle and Cell DivisionMeiosis	Class 11: Cell Cycle and Cell Division	Single correctEasy
A easy single correct question on meiosis, from Cell Cycle and Cell Division. NCERT: Class 11: Cell Cycle and Cell Division In anaphase I the homologous chromosomes separate, but the sister chromatids stay joined at their centromeres. In anaphase II the centromere of each chromosome splits (it is held by kinetochore fibres from both poles), allowing the sister chromatids to move to opposite poles. Metaphases only align chromosomes, and telophase reforms nuclei. Answer: (3).
125	Biodiversity and ConservationConservation strategies	Class 12: Biodiversity and Conservation	Single correctEasy
A easy single correct question on conservation strategies, from Biodiversity and Conservation. NCERT: Class 12: Biodiversity and Conservation The historic Convention on Biological Diversity, 'The Earth Summit', was held in Rio de Janeiro in 1992. It called on all nations to take measures for conservation of biodiversity and sustainable use of its benefits. The World Summit on Sustainable Development followed in 2002 in Johannesburg. Answer: (2).
126	Photosynthesis in Higher PlantsCalvin cycle	Class 11: Photosynthesis in Higher Plants	Single correctEasy
A easy single correct question on calvin cycle, from Photosynthesis in Higher Plants. NCERT: Class 11: Photosynthesis in Higher Plants To fix one CO$_2$ the Calvin cycle uses 3 ATP (2 in reduction of PGA, 1 in regeneration of RuBP) and 2 NADPH. One glucose (C$_6$) needs six turns of the cycle: ATP: $6 \times 3 = 18$ NADPH: $6 \times 2 = 12$ So 18 ATP and 12 NADPH. Answer: (2).
127	EcosystemProductivity and decomposition	Class 12: Ecosystem	Single correctEasy
A easy single correct question on productivity and decomposition, from Ecosystem. NCERT: Class 12: Ecosystem Gross primary productivity is the rate of production of organic matter during photosynthesis. Part of it is used by the plants themselves in respiration. What remains, gross primary productivity minus respiration losses (R), is the net primary productivity available to heterotrophs: GPP − R = NPP. Answer: (3).
129	Molecular Basis of InheritanceTranscription and translation	Class 12: Molecular Basis of Inheritance	Single correctEasy
A easy single correct question on transcription and translation, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance Eukaryotic nuclei have three RNA polymerases: - RNA polymerase I transcribes rRNAs (28S, 18S and 5.8S); - RNA polymerase II transcribes the precursor of mRNA, hnRNA; - RNA polymerase III transcribes tRNA, 5S rRNA and snRNAs. Answer: (2).
130	Sexual Reproduction in Flowering PlantsPollination and outbreeding devices	Class 12: Sexual Reproduction in Flowering Plants	Single correctEasy
A easy single correct question on pollination and outbreeding devices, from Sexual Reproduction in Flowering Plants. NCERT: Class 12: Sexual Reproduction in Flowering Plants Maize is wind pollinated. The 'tassels' seen on the corn cob are the long stigmas and styles, which wave in the wind to trap pollen grains. Wind-pollinated flowers often have large, feathery stigmas for this purpose. Answer: (2).
131	Plant KingdomBryophytes and pteridophytes	Class 11: Plant Kingdom	Single correctEasy
A easy single correct question on bryophytes and pteridophytes, from Plant Kingdom. NCERT: Class 11: Plant Kingdom Most pteridophytes are homosporous (one kind of spore). Genera like Selaginella and Salvinia are heterosporous: they produce large megaspores and small microspores, which give rise to female and male gametophytes. Lycopodium, Psilotum and Equisetum are homosporous, so each other option pairs a homosporous genus with a heterosporous one. Answer: (2).
133	Anatomy of Flowering PlantsTissue systems	Class 11: Anatomy of Flowering Plants	StatementsMedium
A medium statements question on tissue systems, from Anatomy of Flowering Plants. NCERT: Class 11: Anatomy of Flowering Plants Statement I: endarch and exarch describe the position of the primary xylem: protoxylem towards the centre (pith) and metaxylem towards the periphery is endarch, as in stems; protoxylem towards the periphery and metaxylem towards the centre is exarch, as in roots. They are not used for secondary xylem. Incorrect. Statement II: in roots the primary xylem is exarch. Correct. Answer: (4).
134	Principles of Inheritance and VariationLinkage and recombination	Class 12: Principles of Inheritance and Variation	Single correctEasy
A easy single correct question on linkage and recombination, from Principles of Inheritance and Variation. NCERT: Class 12: Principles of Inheritance and Variation Morgan found that genes on the same chromosome are linked and that some recombination occurs between them. His student Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between them, and mapped their positions: the first genetic maps. Sutton and Boveri proposed the chromosomal theory of inheritance; Henking observed the X body in insects. Answer: (3).
135	Respiration in PlantsGlycolysis	Class 11: Respiration in Plants	Assertion and reasonEasy
A easy assertion and reason question on glycolysis, from Respiration in Plants. NCERT: Class 11: Respiration in Plants In glycolysis ATP is consumed at two steps: 1. Glucose is phosphorylated to glucose-6-phosphate by hexokinase. 2. Fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate by phosphofructokinase. So A is true, and R names exactly those two steps, which is why A is true. R correctly explains A. Answer: (1).
136	Environmental IssuesOzone depletion	No matching NCERT chapter	Single correctEasy
A easy single correct question on ozone depletion, from Environmental Issues. NCERT: No matching NCERT chapter (1) True. Microbes decomposing the organic matter of sewage use up much dissolved oxygen (a high BOD), and fish and other aquatic organisms die. (2) Not correct. An algal bloom, the excess growth of planktonic algae caused by nutrients in the water, deteriorates water quality: it gives a colour, smell and toxins and kills fish. It does not promote fisheries. (3) True. Water hyacinth, the 'terror of Bengal', grows abundantly in eutrophic water and upsets the balance of the water body. (4) True. This is biomagnification: toxic substances such as mercury and DDT increase in concentration at successive trophic levels. Answer: (2).
137	Molecular Basis of InheritanceTranscription and translation	Class 12: Molecular Basis of Inheritance	Single correctMedium
A medium single correct question on transcription and translation, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance The ribosome, the cellular factory for protein synthesis, consists of structural RNAs and about 80 different proteins. In its inactive state it exists as two subunits, a large and a small one, which come together when the small subunit meets an mRNA. Answer: (1).
138	Principles of Inheritance and VariationGenetic disorders	Class 12: Principles of Inheritance and Variation	StatementsMedium
A medium statements question on genetic disorders, from Principles of Inheritance and Variation. NCERT: Class 12: Principles of Inheritance and Variation Klinefelter's syndrome is caused by an extra X chromosome: karyotype 47, XXY. A. Incorrect. Langdon Down described Down's syndrome (trisomy 21) in 1866. B. Correct. The individual has an overall masculine development, but feminine development (development of breasts, gynaecomastia) is also expressed. C. Incorrect. Short stature belongs to Down's syndrome (and Turner's); Klinefelter individuals are usually tall. D. Incorrect. Retarded physical, psychomotor and mental development describes Down's syndrome. E. Correct. Such individuals are sterile. So B and E only. Answer: (3).
139	Respiration in PlantsKrebs cycle	Class 11: Respiration in Plants	MatchingEasy
A easy matching question on krebs cycle, from Respiration in Plants. NCERT: Class 11: Respiration in Plants A. The oxidative decarboxylation of pyruvate to acetyl CoA is catalysed by pyruvate dehydrogenase (II). B. Glycolysis is also called the EMP (Embden–Meyerhof–Parnas) pathway (IV). C. Oxidative phosphorylation is ATP synthesis driven by the electron transport system (III). D. The tricarboxylic acid cycle begins when citrate synthase condenses acetyl CoA with oxaloacetate to form citric acid (I). So A-II, B-IV, C-III, D-I. Answer: (4).
140	Morphology of Flowering PlantsFlower and fruit	Class 11: Morphology of Flowering Plants	Assertion and reasonMedium
A medium assertion and reason question on flower and fruit, from Morphology of Flowering Plants. NCERT: Class 11: Morphology of Flowering Plants The flower is a modified shoot. When a shoot tip turns into a flower, the shoot apical meristem changes into a floral meristem. The internodes do not elongate and the axis gets condensed, and the apex produces the different floral appendages (sepals, petals, stamens, carpels) laterally at successive nodes instead of leaves. A is true. R is true, and it is the account of how the shoot is modified, which is why the flower counts as a modified shoot. R correctly explains A. Answer: (1).
141	Plant KingdomGymnosperms	Class 11: Plant Kingdom	Assertion and reasonMedium
A medium assertion and reason question on gymnosperms, from Plant Kingdom. NCERT: Class 11: Plant Kingdom A is true: in gymnosperms the pollen grains are released from the microsporangia and are carried in air currents until they come in contact with the opening of the ovules borne on the megasporophylls. R is false: the pollen does not reach the archegonia. At the ovule, a pollen tube carrying the male gametes grows towards the archegonia and discharges its contents near their mouth. A pollen tube is formed. Answer: (3).
142	Transport in PlantsWater movement in plants	No matching NCERT chapter	MatchingMedium
A medium matching question on water movement in plants, from Transport in Plants. NCERT: No matching NCERT chapter A. Cohesion is the mutual attraction between water molecules (II). B. Adhesion is the attraction of water molecules to polar surfaces, such as the walls of tracheary elements (IV). C. Surface tension: water molecules are attracted to each other more in the liquid phase than in the gas phase (I). D. Guttation is the loss of water in liquid form, as drops from hydathodes at leaf tips, under root pressure (III). So A-II, B-IV, C-I, D-III. Answer: (1).
143	Photosynthesis in Higher PlantsLight reaction	Class 11: Photosynthesis in Higher Plants	Single correctEasy
A easy single correct question on light reaction, from Photosynthesis in Higher Plants. NCERT: Class 11: Photosynthesis in Higher Plants In the chemiosmotic hypothesis, ATP synthesis is linked to a proton gradient across a membrane (the thylakoid membrane in chloroplasts, the inner mitochondrial membrane in mitochondria). Chemiosmosis needs: - a membrane, - a proton pump (electron transport moves protons across it), - a proton gradient, and - ATP synthase, through whose CF$_0$ channel the protons flow back, driving ATP synthesis by CF$_1$. There is no electron gradient in the mechanism and no 'NADP synthase'. Answer: (1).
145	Anatomy of Flowering PlantsAnatomy of root, stem and leaf	Class 11: Anatomy of Flowering Plants	StatementsHard
A hard statements question on anatomy of root, stem and leaf, from Anatomy of Flowering Plants. NCERT: Class 11: Anatomy of Flowering Plants A. Correct. Lenticels are lens-shaped openings in the periderm that permit the exchange of gases between the outer atmosphere and the internal tissue of the stem. B. Incorrect. Bark formed early in the season is early or soft bark; that formed towards the end of the season is late or hard bark. C. Incorrect. Bark is a non-technical term that refers to all tissues exterior to the vascular cambium. The statement calls it a technical term. D. Correct. Bark therefore includes the periderm and the secondary phloem. E. Incorrect. The phellogen (cork cambium) is a couple of layers thick. So A and D only. Answer: (2).
146	Cell Cycle and Cell DivisionMitosis	Class 11: Cell Cycle and Cell Division	MatchingEasy
A easy matching question on mitosis, from Cell Cycle and Cell Division. NCERT: Class 11: Cell Cycle and Cell Division A. M phase in a somatic cell is mitosis, the equational division (IV). B. In G$_2$ proteins are synthesised in preparation for mitosis while cell growth continues (I). C. The quiescent stage (G$_0$) is an inactive stage in which cells remain metabolically active but no longer proliferate (II). D. G$_1$ is the interval between mitosis and the initiation of DNA replication (III). So A-IV, B-I, C-II, D-III. Answer: (3).
147	Organisms and PopulationsInteractions	Class 12: Organisms and Populations	MatchingEasy
A easy matching question on interactions, from Organisms and Populations. NCERT: Class 12: Organisms and Populations A. Mutualism: both species benefit, +/+ (IV). B. Commensalism: one benefits and the other is neither harmed nor benefited, +/0 (I). C. Amensalism: one is harmed and the other unaffected, −/0 (II). D. Parasitism: the parasite benefits and the host is harmed, +/− (III). So A-IV, B-I, C-II, D-III. Answer: (2).
148	Organisms and PopulationsInteractions	Class 12: Organisms and Populations	StatementsEasy
A easy statements question on interactions, from Organisms and Populations. NCERT: Class 12: Organisms and Populations Statement I is Gause's competitive exclusion principle as stated: two closely related species competing for the same resources cannot co-exist indefinitely, and the competitively inferior one will be eliminated eventually. True. Statement II reverses the observation: in general, herbivores and plants appear to be more adversely affected by competition than carnivores. False. Answer: (3).
149	Mineral NutritionEssential elements and their functions	No matching NCERT chapter	MatchingMedium
A medium matching question on essential elements and their functions, from Mineral Nutrition. NCERT: No matching NCERT chapter A. Iron is an important constituent of ferredoxin and cytochromes and activates the catalase enzyme (III). B. Zinc activates carboxylases and is needed in the synthesis of auxin (I). C. Boron is required for uptake and utilisation of Ca$^{2+}$, pollen germination, and cell elongation and differentiation (IV). D. Molybdenum is a component of nitrate reductase and nitrogenase (II). So A-III, B-I, C-IV, D-II. Answer: (3).
153	Environmental IssuesOzone depletion	No matching NCERT chapter	Single correctEasy
A easy single correct question on ozone depletion, from Environmental Issues. NCERT: No matching NCERT chapter (1) Incorrect. Eutrophication is the natural ageing of a lake by nutrient enrichment (nitrates, phosphates), which encourages plant and algal growth; it is not the increase of sewage itself. (2) Correct. Biomagnification is the increase in concentration of a toxicant (DDT, mercury) at successive trophic levels, because the toxicant is not metabolised or excreted and passes up the food chain. (3) Incorrect. A large amount of nutrients in water causes algal blooms; it does not restrict them. (4) Incorrect. Algal blooms deplete oxygen and release toxins, so they increase fish mortality. Answer: (2).
154	Principles of Inheritance and VariationGenetic disorders	Class 12: Principles of Inheritance and Variation	Single correctEasy
A easy single correct question on genetic disorders, from Principles of Inheritance and Variation. NCERT: Class 12: Principles of Inheritance and Variation In pedigree symbols a square is a male and a circle a female; a filled symbol is an affected individual. (1) A single horizontal line between a male and a female is an ordinary mating. (2) A double line between them is a consanguineous mating: mating between relatives. (3) Parents joined by a line, with a vertical line down to a filled square, show parents with an affected son (offspring). (4) Filled square, circle and diamond are affected individuals (male, female, sex unspecified). So the double line, option (2), shows mating between relatives. Answer: (2).
159	Cell: The Unit of LifeCell organelles	Class 11: Cell: The Unit of Life	StatementsEasy
A easy statements question on cell organelles, from Cell: The Unit of Life. NCERT: Class 11: Cell: The Unit of Life The endomembrane system is the group of membranous organelles whose functions are coordinated: the endoplasmic reticulum, Golgi complex, lysosomes and vacuoles. Mitochondria, chloroplasts and peroxisomes work independently and are not part of it. So A, C and E are not in the endomembrane system. Answer: (2).
160	Molecular Basis of InheritanceDNA structure	Class 12: Molecular Basis of Inheritance	StatementsEasy
A easy statements question on dna structure, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance RNA is less stable than DNA: its 2'-OH group makes it reactive, and it lacks the proofreading and repair that protect DNA. So RNA mutates at a faster rate (Statement I true). Consequently viruses with an RNA genome, which also have a shorter life span, mutate and evolve faster (Statement II true). Answer: (1).
167	Organisms and PopulationsInteractions	Class 12: Organisms and Populations	MatchingEasy
A easy matching question on interactions, from Organisms and Populations. NCERT: Class 12: Organisms and Populations A. A leopard and a lion in the same forest or grassland hunt the same prey: competition (I). B. The cuckoo lays its eggs in the crow's nest and the crow raises the young: brood parasitism (II). C. In mycorrhizae the fungus helps the plant absorb nutrients and the plant gives it carbohydrates: mutualism (III). D. The cattle egret feeds on insects stirred up by grazing cattle, which are unaffected: commensalism (IV). So A-I, B-II, C-III, D-IV. Answer: (1).
169	Molecular Basis of InheritanceDNA structure	Class 12: Molecular Basis of Inheritance	StatementsEasy
A easy statements question on dna structure, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance Statement I: in prokaryotes the DNA is negatively charged (its phosphate groups) and is held with some positively charged proteins in the nucleoid. The statement reverses the charges. False. Statement II: in eukaryotes the negatively charged DNA is wrapped around a positively charged histone octamer (histones are rich in lysine and arginine) to form the nucleosome. True. Answer: (4).
177	Molecular Basis of InheritanceLac operon	Class 12: Molecular Basis of Inheritance	MatchingEasy
A easy matching question on lac operon, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance In the lac operon: - the z gene codes for $\beta$-galactosidase, which hydrolyses lactose into galactose and glucose; - the y gene codes for permease, which increases the permeability of the cell to lactose; - the a gene codes for transacetylase; - the regulatory i gene codes for the repressor protein. So A (a) - II, B (y) - III, C (i) - IV, D (z) - I. Answer: (2).
179	Cell: The Unit of LifeCytoskeleton, cilia and flagella	Class 11: Cell: The Unit of Life	Single correctEasy
A easy single correct question on cytoskeleton, cilia and flagella, from Cell: The Unit of Life. NCERT: Class 11: Cell: The Unit of Life The cytoskeleton, an elaborate network of protein filaments (microtubules, microfilaments and intermediate filaments) in the cytoplasm, is involved in many functions such as mechanical support, motility and maintenance of the shape of the cell. Of the options, motility is the function the textbook names. Protein synthesis is done by ribosomes. Spindle microtubules do take part in nuclear division, but motility is the function attributed to the cytoskeleton as such. Answer: (3).
181	Environmental IssuesOzone depletion	No matching NCERT chapter	StatementsEasy
A easy statements question on ozone depletion, from Environmental Issues. NCERT: No matching NCERT chapter Statement I: the electrostatic precipitator is the most widely used device for removing particulate matter, and it is used in the exhausts of thermal power plants. Correct. Statement II: it removes particulate matter (over 99 per cent of it): electrodes give the dust particles a negative charge and they are attracted to collecting plates. It does not remove ionising radiations. Incorrect. Answer: (3).
182	Principles of Inheritance and VariationGenetic disorders	Class 12: Principles of Inheritance and Variation	Single correctEasy
A easy single correct question on genetic disorders, from Principles of Inheritance and Variation. NCERT: Class 12: Principles of Inheritance and Variation Down's syndrome is caused by an extra copy of chromosome 21 (trisomy 21). The affected person is short statured with a small round head, a furrowed tongue and partially open mouth, and a broad palm with a characteristic palm crease; physical, psychomotor and mental development is retarded. Turner's syndrome (XO) and Klinefelter's syndrome (XXY) are sex-chromosome disorders without this sign; thalassemia is a blood disorder. Answer: (1).
186	Organisms and PopulationsPopulation growth models	Class 12: Organisms and Populations	MatchingEasy
A easy matching question on population growth models, from Organisms and Populations. NCERT: Class 12: Organisms and Populations A. Logistic (Verhulst–Pearl) growth is the realistic model when resources are limited; growth levels off at the carrying capacity (II). B. Exponential growth happens when resources are unlimited (I). C. In an expanding (growing) population the pre-reproductive group is the largest, followed by the reproductive and post-reproductive groups: a broad-based triangular pyramid (III). D. In a stable population the pre-reproductive and reproductive groups are about the same: a bell-shaped pyramid (IV). So A-II, B-I, C-III, D-IV. Answer: (1).
191	Cell Cycle and Cell DivisionMeiosis	Class 11: Cell Cycle and Cell Division	StatementsMedium
A medium statements question on meiosis, from Cell Cycle and Cell Division. NCERT: Class 11: Cell Cycle and Cell Division A. Incorrect. Chromosomes only become visible and compact in leptotene; the bivalents (tetrads) form after synapsis in zygotene and are clearly seen in pachytene. B. Correct. In (mitotic) anaphase the centromeres split and the chromatids separate and move to opposite poles. C. Incorrect. Terminalisation of chiasmata takes place in diakinesis. D. Correct. In telophase the nucleolus, Golgi complex and ER reform. E. Incorrect. Crossing over is between non-sister chromatids of homologous chromosomes. So B and D only. Answer: (2).
194	Molecular Basis of InheritanceTranscription and translation	Class 12: Molecular Basis of Inheritance	Single correctMedium
A medium single correct question on transcription and translation, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance The mRNA is complementary to the template strand, so it has the same sequence and polarity as the coding strand, with uracil in place of thymine. mRNA: 5' AUCG AUCG AUCG AUCG AUCG AUCG AUCG 3' Coding strand: 5' ATCG ATCG ATCG ATCG ATCG ATCG ATCG 3' Option (3) is exactly this, read 5' to 3'. (1) and (2) contain U, so they are RNA, not DNA (and they are complementary, not identical, to the mRNA). (4) has the right letters but written 3' to 5', so the polarity is reversed. Answer: (3).
196	Cell Cycle and Cell DivisionMitosis	Class 11: Cell Cycle and Cell Division	StatementsEasy
A easy statements question on mitosis, from Cell Cycle and Cell Division. NCERT: Class 11: Cell Cycle and Cell Division Statement I: cells in the quiescent stage (G$_0$) remain metabolically active but no longer proliferate unless called on to do so. Incorrect. Statement II: in animal cells, during the S phase DNA replication begins in the nucleus and the centriole duplicates in the cytoplasm, so the centrosome is duplicated in S phase. Correct. Answer: (4).

Zoology questions, each with its chapter and our explanation
Q	Chapter and topic	NCERT	Kind and level
108	Biotechnology: Principles and ProcessesrDNA technology	Class 12: Biotechnology: Principles and Processes	Single correctEasy
A easy single correct question on rdna technology, from Biotechnology: Principles and Processes. NCERT: Class 12: Biotechnology: Principles and Processes After gel electrophoresis, DNA fragments are invisible until stained. They are stained with ethidium bromide and then exposed to UV radiation: the DNA bands appear as bright orange coloured bands. The bands can then be cut out of the gel and the DNA extracted (elution). Answer: (4).
116	BiomoleculesCarbohydrates, lipids and nucleic acids	Class 11: Biomolecules	Single correctEasy
A easy single correct question on carbohydrates, lipids and nucleic acids, from Biomolecules. NCERT: Class 11: Biomolecules Starch forms helical secondary structures, and iodine (I$_2$) molecules are held inside the helices, giving the blue colour. Cellulose is a straight-chain polymer of glucose with no complex helices, so it cannot hold I$_2$ and gives no blue colour. Cellulose is a polysaccharide, not a disaccharide, and it is not broken down by iodine. Answer: (3).
128	Biotechnology: Principles and ProcessesrDNA technology	Class 12: Biotechnology: Principles and Processes	Single correctEasy
A easy single correct question on rdna technology, from Biotechnology: Principles and Processes. NCERT: Class 12: Biotechnology: Principles and Processes To isolate DNA, cells are broken open and the other macromolecules removed: RNA by ribonuclease, proteins (including histones) by protease, and cell wall polysaccharides by enzymes such as cellulase or chitinase. Purified DNA then precipitates out after the addition of chilled ethanol, seen as a collection of fine threads in the suspension. Answer: (2).
132	Biotechnology: Principles and ProcessesrDNA technology	Class 12: Biotechnology: Principles and Processes	Single correctEasy
A easy single correct question on rdna technology, from Biotechnology: Principles and Processes. NCERT: Class 12: Biotechnology: Principles and Processes In biolistics (the gene gun), plant cells are bombarded with high-velocity micro-particles of gold or tungsten coated with DNA. These metals are dense and chemically inert, so the coated particles carry the DNA into the cells without reacting with it. Answer: (3).
144	BiomoleculesEnzymes	Class 11: Biomolecules	Single correctEasy
A easy single correct question on enzymes, from Biomolecules. NCERT: Class 11: Biomolecules Malonate closely resembles succinate, the substrate of succinic dehydrogenase, in its structure. It binds to the enzyme's active site and blocks it: competitive inhibition. Competitive inhibitors of this kind are used to control bacterial pathogens, and malonate inhibiting succinic dehydrogenase is the standard example. Answer: (1).
150	Biotechnology: Principles and ProcessesrDNA technology	Class 12: Biotechnology: Principles and Processes	Single correctMedium
A medium single correct question on rdna technology, from Biotechnology: Principles and Processes. NCERT: Class 12: Biotechnology: Principles and Processes The processes of recombinant DNA technology run: isolation of DNA, fragmentation of the DNA by restriction endonucleases, isolation of the desired DNA fragment, amplification of the gene of interest (PCR), ligation into a vector, and insertion of the recombinant DNA into the host. Among the four steps given, the DNA is first cut at specific locations by a restriction enzyme (B). The fragment carrying the gene of interest is then separated (gel electrophoresis) and isolated (C). It is amplified by PCR (D), and the recombinant DNA is finally introduced into the host cell (A). So B, C, D, A. Answer: (1).
151	Reproductive HealthContraception	Class 12: Reproductive Health	MatchingEasy
A easy matching question on contraception, from Reproductive Health. NCERT: Class 12: Reproductive Health A. Vasectomy, cutting and tying the vas deferens, is a surgical method (sterilisation) (III). B. Coitus interruptus, withdrawal before ejaculation, is a natural method (IV). C. Cervical caps cover the cervix and stop sperm meeting the ovum: a barrier method (II). D. Saheli, a once-a-week non-steroidal pill, is an oral contraceptive (I). So A-III, B-IV, C-II, D-I. Answer: (2).
152	Human ReproductionMale and female reproductive systems	Class 12: Human Reproduction	StatementsEasy
A easy statements question on male and female reproductive systems, from Human Reproduction. NCERT: Class 12: Human Reproduction Statement I: the vas deferens ascends into the abdomen, loops over the urinary bladder, receives a duct from the seminal vesicle and opens into the urethra as the ejaculatory duct. True. Statement II: the cavity of the cervix is the cervical canal, which along with the vagina forms the birth canal. True. Both statements are true. Answer: (1).
155	Reproductive HealthSTDs	Class 12: Reproductive Health	Single correctEasy
A easy single correct question on stds, from Reproductive Health. NCERT: Class 12: Reproductive Health Except for hepatitis B, genital herpes and HIV infection, the other STDs are completely curable if detected early and treated properly. Gonorrhoea, a bacterial infection, is the one in the list that is completely curable. Answer: (2).
156	Human Health and DiseaseCancer and drug abuse	Class 12: Human Health and Disease	MatchingEasy
A easy matching question on cancer and drug abuse, from Human Health and Disease. NCERT: Class 12: Human Health and Disease A. Heroin (smack) is a depressant that slows down body functions (II). B. Cannabinoids such as marijuana affect the cardiovascular system of the body (I). C. Cocaine interferes with the transport of the neurotransmitter dopamine (IV). D. Morphine is a very effective sedative and painkiller (III). So A-II, B-I, C-IV, D-III. Answer: (1).
157	Locomotion and MovementJoints and disorders	Class 11: Locomotion and Movement	MatchingEasy
A easy matching question on joints and disorders, from Locomotion and Movement. NCERT: Class 11: Locomotion and Movement A. Cartilaginous joints, such as those between adjacent vertebrae, allow limited movement (II). B. A ball and socket joint lies between the humerus and the pectoral girdle (IV). C. Fibrous joints, the sutures between the flat skull bones, allow no movement (I). D. A saddle joint lies between the carpal and metacarpal of the thumb (III). So A-II, B-IV, C-I, D-III. Answer: (2).
158	BiomoleculesProteins and amino acids	Class 11: Biomolecules	StatementsEasy
A easy statements question on proteins and amino acids, from Biomolecules. NCERT: Class 11: Biomolecules Statement I: a protein is imagined as a line whose left end is the first amino acid, the N-terminal amino acid, and whose right end is the last amino acid, the C-terminal amino acid. The statement swaps the two ends. False. Statement II: adult human haemoglobin has quaternary structure: four subunits, two of $\alpha$ type and two of $\beta$ type. True. Answer: (4).
161	Chemical Coordination and IntegrationHormone mechanism	Class 11: Chemical Coordination and Integration	MatchingMedium
A medium matching question on hormone mechanism, from Chemical Coordination and Integration. NCERT: Class 11: Chemical Coordination and Integration Read List II as the organ each hormone acts on (or, for ANF, comes from): A. Cholecystokinin (CCK) acts on the pancreas (and gall bladder), stimulating pancreatic enzyme secretion and bile release (IV). B. Gastric inhibitory peptide (GIP) inhibits gastric secretion: it acts on the gastric glands (III). C. Atrial natriuretic factor (ANF) is secreted by the atrial wall of the heart (II). D. ADH acts on the distal parts of the kidney tubule, increasing water reabsorption (I). So A-IV, B-III, C-II, D-I. Answer: (1).
162	Human ReproductionMenstrual cycle	Class 12: Human Reproduction	Assertion and reasonMedium
A medium assertion and reason question on menstrual cycle, from Human Reproduction. NCERT: Class 12: Human Reproduction A is true: the blastocyst becomes embedded in the endometrium of the uterus (implantation), and the thickened endometrium, maintained by progesterone, is necessary for it. R is true: if fertilisation does not occur, the corpus luteum degenerates; progesterone falls, and the endometrium disintegrates, giving menstruation. But R describes what happens without fertilisation; it does not explain why the endometrium is needed for implantation. So R is not the correct explanation of A. Answer: (2).
163	Human Health and DiseasePathogens and diseases	Class 12: Human Health and Disease	MatchingEasy
A easy matching question on pathogens and diseases, from Human Health and Disease. NCERT: Class 12: Human Health and Disease A. Ringworm is a fungal infection, caused by Microsporum, Trichophyton and Epidermophyton (II). B. Filariasis (elephantiasis) is caused by the filarial worm Wuchereria bancrofti (III). C. Malaria is caused by Plasmodium, for example P. vivax (IV). D. Pneumonia is caused by Streptococcus pneumoniae and Haemophilus influenzae (I). So A-II, B-III, C-IV, D-I. Answer: (1).
164	BiomoleculesEnzymes	Class 11: Biomolecules	StatementsEasy
A easy statements question on enzymes, from Biomolecules. NCERT: Class 11: Biomolecules Statement I: enzymes work best at an optimum temperature. Low temperature keeps an enzyme in a temporarily inactive state, from which it recovers on warming; high temperature destroys enzyme activity because the protein is denatured by heat. True. Statement II: an inhibitor that closely resembles the substrate in its molecular structure competes with it for the active site and inhibits the enzyme; it is a competitive inhibitor (for example malonate for succinic dehydrogenase). True. Answer: (1).
165	Animal KingdomNon-chordate phyla	Class 11: Animal Kingdom	MatchingMedium
A medium matching question on non-chordate phyla, from Animal Kingdom. NCERT: Class 11: Animal Kingdom Each organism with its excretory or osmoregulatory structure: A. Taenia (tapeworm, a flatworm): flame cells (protonephridia) (III). B. Paramoecium: contractile vacuole, which removes excess water (II). C. Periplaneta (cockroach): Malpighian tubules, helped by the urecose glands, fat body and nephrocytes (IV). D. Pheretima (earthworm, an annelid): nephridia (I). So A-III, B-II, C-IV, D-I. Answer: (3).
166	Biotechnology and its ApplicationsGene therapy	Class 12: Biotechnology and its Applications	Single correctMedium
A medium single correct question on gene therapy, from Biotechnology and its Applications. NCERT: Class 12: Biotechnology and its Applications Early diagnosis needs the pathogen to be detected when its numbers are still very low, before symptoms appear. Conventional methods such as serum and urine analysis cannot do this: they detect a disease only after the pathogen has multiplied and symptoms have appeared. Molecular diagnosis can: recombinant DNA technology (probes), PCR (which amplifies even a very small amount of pathogen nucleic acid) and ELISA (antigen–antibody detection) all serve early diagnosis. Answer: (2).
168	Structural Organisation in AnimalsAnimal tissues	Class 11: Structural Organisation in Animals	StatementsEasy
A easy statements question on animal tissues, from Structural Organisation in Animals. NCERT: Class 11: Structural Organisation in Animals Statement I: tendons and ligaments are examples of dense regular connective tissue, with collagen fibres in parallel bundles. Dense irregular tissue is found in the skin. False. Statement II: cartilage is a specialised connective tissue (with bone and blood), not dense regular tissue. False. Both statements are false. Answer: (2).
170	Neural Control and CoordinationPeripheral and visceral nervous system	Class 11: Neural Control and Coordination	MatchingEasy
A easy matching question on peripheral and visceral nervous system, from Neural Control and Coordination. NCERT: Class 11: Neural Control and Coordination A. The fovea, a thinned-out part of the retina with only cones, is the point of greatest visual acuity (III). B. The iris is the visible coloured portion of the eye; it regulates the diameter of the pupil (I). C. The blind spot is where the optic nerve leaves the eye; there are no photoreceptors there (IV). D. The sclera is the external layer of the eye, formed of dense connective tissue (II). So A-III, B-I, C-IV, D-II. Answer: (1).
171	EvolutionEvidences of evolution	Class 12: Evolution	Single correctEasy
A easy single correct question on evidences of evolution, from Evolution. NCERT: Class 12: Evolution Australian marsupials radiated from one ancestral stock into many forms: the numbat (anteater), spotted cuscus, flying phalanger, Tasmanian wolf, Tasmanian tiger cat, marsupial mole, koala, wombat, kangaroo and others. Option (2) has three marsupials. Each other option includes placental mammals: bobcat (1); mole and flying squirrel (3); lemur, anteater and wolf (4). These are the placental counterparts that show convergent evolution with the marsupials. Answer: (2).
172	Human ReproductionMenstrual cycle	Class 12: Human Reproduction	StatementsEasy
A easy statements question on menstrual cycle, from Human Reproduction. NCERT: Class 12: Human Reproduction A. Correct. In non-primate mammals (cows, sheep, rats, dogs) the reproductive cycle is the oestrus cycle; primates have a menstrual cycle. B. Incorrect. The first menstruation at puberty is menarche; menopause is when it stops, around 50 years. C. Correct. Lack of menstruation may indicate pregnancy (it may also come from stress or poor health). D. Correct. Cyclic menstruation extends between menarche and menopause. So A, C and D only. Answer: (4).
173	Breathing and Exchange of GasesMechanism and regulation of breathing	Class 11: Breathing and Exchange of Gases	Single correctEasy
A easy single correct question on mechanism and regulation of breathing, from Breathing and Exchange of Gases. NCERT: Class 11: Breathing and Exchange of Gases Vital capacity is the maximum volume of air a person can breathe in after a forced expiration (or breathe out after a forced inspiration). It includes the expiratory reserve volume, the tidal volume and the inspiratory reserve volume: VC = ERV + TV + IRV. IRV + ERV + TV + RV is the total lung capacity; IRV + ERV leaves out the tidal volume. Answer: (4).
174	Body Fluids and CirculationECG	Class 11: Body Fluids and Circulation	MatchingEasy
A easy matching question on ecg, from Body Fluids and Circulation. NCERT: Class 11: Body Fluids and Circulation A. The P-wave is the electrical excitation (depolarisation) of the atria, which leads to atrial contraction (III). B. The Q-wave marks the beginning of ventricular systole (I). C. The QRS complex is the depolarisation of the ventricles, which starts their contraction (IV). D. The T-wave is the repolarisation of the ventricles (II). So A-III, B-I, C-IV, D-II. Answer: (1).
175	Reproductive HealthAmniocentesis and MTP	Class 12: Reproductive Health	Assertion and reasonEasy
A easy assertion and reason question on amniocentesis and mtp, from Reproductive Health. NCERT: Class 12: Reproductive Health A is false: a statutory ban on amniocentesis for sex determination, to legally check the increasing menace of female foeticide, is one of the strategies of the Reproductive and Child Health Care (RCH) programme. Amniocentesis for sex determination is banned, not promoted. R is true: the ban checks female foeticide. Answer: (4).
176	Digestion and AbsorptionHuman digestive system	No matching NCERT chapter	Single correctEasy
A easy single correct question on human digestive system, from Digestion and Absorption. NCERT: No matching NCERT chapter The ileum opens into the caecum of the large intestine. The ileo-caecal valve at this junction prevents the backflow of the faecal matter from the caecum into the ileum. The sphincter of Oddi guards the common hepato-pancreatic duct; the gastro-oesophageal sphincter controls the opening of the oesophagus into the stomach; the pyloric sphincter guards the opening of the stomach into the duodenum. Answer: (2).
178	Digestion and AbsorptionHuman digestive system	No matching NCERT chapter	MatchingEasy
A easy matching question on human digestive system, from Digestion and Absorption. NCERT: No matching NCERT chapter A. Peptic (chief) cells of the gastric glands secrete the proenzyme pepsinogen (III). B. Goblet cells secrete mucus (I). C. Oxyntic (parietal) cells secrete HCl and the intrinsic factor needed to absorb vitamin B$_{12}$ (IV). D. Hepatic cells of the liver secrete bile (II). So A-III, B-I, C-IV, D-II. Answer: (3).
180	Excretory Products and their EliminationNephron structure	Class 11: Excretory Products and their Elimination	Assertion and reasonEasy
A easy assertion and reason question on nephron structure, from Excretory Products and their Elimination. NCERT: Class 11: Excretory Products and their Elimination A is true: in most nephrons the loop of Henle is too short and extends only very little into the medulla; these are cortical nephrons. In some, the loop is very long and runs deep into the medulla; these are juxtamedullary nephrons. R is false: it reverses the two. Juxtamedullary nephrons have the long loops and cortical nephrons the short ones. Answer: (3).
183	Animal KingdomBasis of classification	Class 11: Animal Kingdom	Single correctEasy
A easy single correct question on basis of classification, from Animal Kingdom. NCERT: Class 11: Animal Kingdom Coelenterates (cnidarians) and ctenophores are radially symmetrical. Echinoderm adults are radially symmetrical (their larvae are bilateral). Hemichordates such as Balanoglossus are bilaterally symmetrical, so radial symmetry is not found in their adults. Answer: (2).
184	Human Health and DiseaseImmunity	Class 12: Human Health and Disease	Single correctEasy
A easy single correct question on immunity, from Human Health and Disease. NCERT: Class 12: Human Health and Disease After entering the body, HIV first infects macrophages, where its RNA is copied into viral DNA by reverse transcriptase and the cell acts as a virus factory. At the same time HIV enters helper T-lymphocytes (T$_H$ cells), replicates and produces progeny viruses, which attack other helper T cells. Their number falls steadily, which is what weakens immunity in AIDS. Answer: (1).
185	Biotechnology: Principles and ProcessesRestriction enzymes and vectors	Class 12: Biotechnology: Principles and Processes	Single correctEasy
A easy single correct question on restriction enzymes and vectors, from Biotechnology: Principles and Processes. NCERT: Class 12: Biotechnology: Principles and Processes BAC (bacterial artificial chromosome), YAC (yeast artificial chromosome) and the plasmid pBR322 are all cloning vectors: they carry a foreign DNA fragment into a host and replicate it. A probe is a single-stranded DNA or RNA tagged with a radioactive or fluorescent label, used to find a complementary sequence by hybridisation; it is not a vector. Answer: (4).
187	Animal KingdomChordate classes	Class 11: Animal Kingdom	StatementsMedium
A medium statements question on chordate classes, from Animal Kingdom. NCERT: Class 11: Animal Kingdom A. Incorrect. Chordates have a single, dorsal, hollow nerve cord; a ventral, solid, double nerve cord is a non-chordate feature. B. Correct. Chordates have a closed circulatory system. C. Correct. Paired pharyngeal gill slits are present (at least in the embryo). D. Incorrect. The heart of chordates is ventral; non-chordates have a dorsal heart, if any. E. Incorrect. Chordates are triploblastic and coelomate, not pseudocoelomate. So B and C only. Answer: (2).
188	Neural Control and CoordinationCentral nervous system	Class 11: Neural Control and Coordination	Single correctEasy
A easy single correct question on central nervous system, from Neural Control and Coordination. NCERT: Class 11: Neural Control and Coordination The inner parts of the cerebral hemispheres and a group of associated deep structures (amygdala, hippocampus and others) form the limbic system. Along with the hypothalamus it is involved in the regulation of sexual behaviour and the expression of emotional reactions such as excitement, pleasure, rage and fear, and in motivation. Corpora quadrigemina are visual and auditory reflex centres of the midbrain; the corpus callosum joins the two hemispheres; the thalamus relays sensory signals. Answer: (1).
189	Animal KingdomChordate classes	Class 11: Animal Kingdom	Single correctEasy
A easy single correct question on chordate classes, from Animal Kingdom. NCERT: Class 11: Animal Kingdom The most unique mammalian characteristic is the presence of mammary glands that nourish the young. Mammals also have hair on the skin and external ears (pinnae), found in no other class. A tympanic membrane is present in frogs, reptiles and birds too; development in mammals is direct; and mammals have a dicondylic skull (reptiles and birds are monocondylic). Answer: (2).
190	Chemical Coordination and IntegrationEndocrine glands	Class 11: Chemical Coordination and Integration	StatementsMedium
A medium statements question on endocrine glands, from Chemical Coordination and Integration. NCERT: Class 11: Chemical Coordination and Integration Thyroid hormones regulate the basal metabolic rate (B), support the process of red blood cell formation (E), control the metabolism of carbohydrates, proteins and fats, and influence the maintenance of water and electrolyte balance (A). C. The normal rhythm of the sleep-wake cycle is regulated by melatonin from the pineal gland. D. The development of the immune system is promoted by thymosins from the thymus. So C and D are not under thyroid control. Answer: (3).
192	Structural Organisation in AnimalsAnimal tissues	Class 11: Structural Organisation in Animals	MatchingEasy
A easy matching question on animal tissues, from Structural Organisation in Animals. NCERT: Class 11: Structural Organisation in Animals A. Mast cells are found in areolar connective tissue, along with fibroblasts and macrophages (II). B. The inner surface of bronchioles is lined by ciliated epithelium, which moves mucus along (I). C. Blood is a specialised connective tissue (IV). D. The tubular parts of the nephron are lined by cuboidal epithelium (III). So A-II, B-I, C-IV, D-III. Answer: (3).
193	Structural Organisation in AnimalsFrog: morphology and anatomy	Class 11: Structural Organisation in Animals	Single correctEasy
A easy single correct question on frog: morphology and anatomy, from Structural Organisation in Animals. NCERT: Class 11: Structural Organisation in Animals In cockroaches both sexes have a brown body, sclerites (the hardened plates of the exoskeleton) and a pair of jointed anal cerci on the 10th segment. Only males have a pair of short, thread-like anal styles. Their presence therefore distinguishes the male: it is the feature of sexual dimorphism. Answer: (2).
195	Structural Organisation in AnimalsFrog: morphology and anatomy	Class 11: Structural Organisation in Animals	StatementsMedium
A medium statements question on frog: morphology and anatomy, from Structural Organisation in Animals. NCERT: Class 11: Structural Organisation in Animals In the cockroach excretion is performed by the Malpighian tubules. In addition, the fat body, nephrocytes and urecose glands also help in excretion. The phallic (conglobate) gland is an accessory reproductive gland of the male, and the collaterial (colleterial) glands of the female secrete the egg case (ootheca). So B, C and D only. Answer: (3).
197	Strategies for Enhancement in Food ProductionAnimal breeding	No matching NCERT chapter	Single correctMedium
A medium single correct question on animal breeding, from Strategies for Enhancement in Food Production. NCERT: No matching NCERT chapter Inbreeding (mating of more closely related individuals for 4–6 generations) increases homozygosity, so it is used to develop pure lines. It exposes harmful recessive genes, which are then eliminated by selection, and it helps accumulate superior genes and eliminate less desirable ones. Options (2) and (3) are these advantages. Continued inbreeding, especially close inbreeding, usually reduces fertility and even productivity: inbreeding depression. Option (4) describes this, which is a disadvantage, so it is not an advantage. Option (1) is not an advantage either, but for a different reason: it is simply untrue, since inbreeding increases homozygosity. Read as 'which effect of inbreeding is not an advantage', the answer is (4). Answer: (4).
198	Excretory Products and their EliminationRegulation and disorders	Class 11: Excretory Products and their Elimination	StatementsMedium
A medium statements question on regulation and disorders, from Excretory Products and their Elimination. NCERT: Class 11: Excretory Products and their Elimination A. Incorrect. An excessive loss of fluid from the body activates (switches on) the osmoreceptors, which stimulate the hypothalamus to release ADH. Osmoreceptors are switched off when body fluid is in excess or after it is restored. B. Correct. ADH facilitates water reabsorption from the later parts of the tubule, preventing diuresis. C. Correct. ANF causes vasodilation, lowering blood pressure. D. Correct. ADH constricts blood vessels, raising blood pressure. E. Incorrect. By raising blood pressure, ADH can increase glomerular blood flow and so the GFR; it does not decrease it. So B, C and D only. Answer: (2).
199	Locomotion and MovementMuscle contraction	Class 11: Locomotion and Movement	StatementsMedium
A medium statements question on muscle contraction, from Locomotion and Movement. NCERT: Class 11: Locomotion and Movement A. Incorrect. A muscle is made of bundles called fascicles, and these are held together by a collagenous connective tissue layer called fascia. The statement gives the bundle's name to the binding layer. B. Correct. The sarcoplasmic reticulum of the muscle fibre is the store house of calcium ions. C. Correct. The light and dark bands, which give the striated appearance, come from the distribution pattern of the actin and myosin proteins. D. Incorrect. The functional unit of contraction, the sarcomere, is the portion of the myofibril between two successive Z lines; the M line is a thin membrane at the middle of the A band. So B and C only. Answer: (2).
200	Body Fluids and CirculationBlood composition	Class 11: Body Fluids and Circulation	StatementsEasy
A easy statements question on blood composition, from Body Fluids and Circulation. NCERT: Class 11: Body Fluids and Circulation A. Incorrect. Basophils are the least abundant leucocytes (0.5–1 per cent); neutrophils are the most abundant (60–65 per cent). B. Correct. Basophils secrete histamine, serotonin and heparin. C. Correct. They are involved in inflammatory reactions. D. Incorrect. A kidney-shaped nucleus is typical of monocytes; basophils have a lobed (often S-shaped) nucleus. E. Incorrect. Basophils are granulocytes, with neutrophils and eosinophils; lymphocytes and monocytes are the agranulocytes. So B and C only. Answer: (3).

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