▶️ Answer/Explanation
Sensitivity is the characteristic of living organisms that describes the ability to detect changes in the environment (stimuli) and produce an appropriate response.
Excretion is the removal of metabolic waste, growth is an increase in size, and movement is change in position — none of these involve detecting and responding to environmental stimuli.
✅ Answer: (D)
Excretion is the removal of metabolic waste, growth is an increase in size, and movement is change in position — none of these involve detecting and responding to environmental stimuli.
✅ Answer: (D)
▶️ Answer/Explanation
The cells shown are ciliated epithelial cells and goblet cells, which are characteristic of the lining of the trachea and bronchi — they produce and sweep mucus to trap pathogens and particles.
These cells are found in the upper airways (trachea/bronchi), not in the alveoli, so the label pointing to those structures is the correct answer (B).
✅ Answer: (B)
These cells are found in the upper airways (trachea/bronchi), not in the alveoli, so the label pointing to those structures is the correct answer (B).
✅ Answer: (B)
▶️ Answer/Explanation
Carbohydrates, fats, and oils all contain only carbon (C), hydrogen (H), and oxygen (O); they do not contain nitrogen.
Proteins are built from amino acids which all contain an amino group \((-NH_2)\), meaning they contain carbon, hydrogen, oxygen, and nitrogen (and sometimes sulfur).
✅ Answer: (D)
Proteins are built from amino acids which all contain an amino group \((-NH_2)\), meaning they contain carbon, hydrogen, oxygen, and nitrogen (and sometimes sulfur).
✅ Answer: (D)
▶️ Answer/Explanation
Statement 1 is incorrect: the graph shows that the reaction still proceeds below 20 ºC (albeit slowly), so enzymes are not denatured below 20 ºC — they simply have lower kinetic energy and activity.
Statement 2 is correct: increasing temperature gives molecules more kinetic energy, so enzyme-substrate collisions are more frequent between 10 ºC and 40 ºC.
Statement 3 is correct: above 40 ºC the rate falls because heat causes the enzyme’s tertiary structure to break down, changing the shape of the active site (denaturation).
✅ Answer: (D)
Statement 2 is correct: increasing temperature gives molecules more kinetic energy, so enzyme-substrate collisions are more frequent between 10 ºC and 40 ºC.
Statement 3 is correct: above 40 ºC the rate falls because heat causes the enzyme’s tertiary structure to break down, changing the shape of the active site (denaturation).
✅ Answer: (D)
▶️ Answer/Explanation
Photosynthesis occurs in the chloroplast, the green organelle found in plant cells that contains the pigment chlorophyll, which absorbs light energy.
The overall equation is \(\text{CO}_2 + \text{H}_2\text{O} \xrightarrow{\text{light}} \text{glucose} + \text{O}_2\); all stages (light-dependent and light-independent reactions) take place within the chloroplast.
✅ Answer: (A)
The overall equation is \(\text{CO}_2 + \text{H}_2\text{O} \xrightarrow{\text{light}} \text{glucose} + \text{O}_2\); all stages (light-dependent and light-independent reactions) take place within the chloroplast.
✅ Answer: (A)
▶️ Answer/Explanation
Inside each villus there are two main absorbing structures: blood capillaries, which absorb the water-soluble products of digestion (glucose and amino acids), and lacteals, which absorb fatty acids and glycerol (the products of fat digestion).
P is the blood capillary (absorbs glucose and amino acids) and Q is the lacteal (absorbs fatty acids and glycerol), making option D the correct row in the table.
✅ Answer: (D)
P is the blood capillary (absorbs glucose and amino acids) and Q is the lacteal (absorbs fatty acids and glycerol), making option D the correct row in the table.
✅ Answer: (D)
▶️ Answer/Explanation
Transpiration is the evaporation of water from plant leaves; it is fastest when the water vapour concentration gradient between the leaf interior and the surrounding air is greatest.
Warm conditions increase evaporation (more kinetic energy), and dry conditions keep the external humidity low, maintaining a steep diffusion gradient — so warm and dry is the fastest combination.
✅ Answer: (C)
Warm conditions increase evaporation (more kinetic energy), and dry conditions keep the external humidity low, maintaining a steep diffusion gradient — so warm and dry is the fastest combination.
✅ Answer: (C)
▶️ Answer/Explanation
When air is breathed into the apparatus, it bubbles through both flasks; exhaled air contains significantly more \(\text{CO}_2\) than inhaled air, which turns limewater milky (due to formation of \(\text{CaCO}_3\) precipitate).
The flask receiving exhaled air turns milky, while the flask receiving inhaled air (which passes atmospheric air through first) shows little or no change — giving result B where only the exhaled side turns milky.
✅ Answer: (B)
The flask receiving exhaled air turns milky, while the flask receiving inhaled air (which passes atmospheric air through first) shows little or no change — giving result B where only the exhaled side turns milky.
✅ Answer: (B)
▶️ Answer/Explanation
Accommodation is the ability of the eye to focus on objects at different distances by adjusting the shape of the lens through the action of the ciliary muscles and suspensory ligaments.
For near objects the lens becomes fatter (more convex), and for distant objects it becomes thinner — this automatic adjustment is called accommodation, not the pupil reflex (which controls light intensity).
✅ Answer: (A)
For near objects the lens becomes fatter (more convex), and for distant objects it becomes thinner — this automatic adjustment is called accommodation, not the pupil reflex (which controls light intensity).
✅ Answer: (A)
▶️ Answer/Explanation
Both asexual and sexual reproduction involve at least one parent organism producing offspring — this is the one universal similarity between the two types of reproduction.
Gametes and fertilisation are exclusive to sexual reproduction, and genetically identical offspring are a feature of asexual reproduction only (sexual reproduction produces genetic variation).
✅ Answer: (B)
Gametes and fertilisation are exclusive to sexual reproduction, and genetically identical offspring are a feature of asexual reproduction only (sexual reproduction produces genetic variation).
✅ Answer: (B)
▶️ Answer/Explanation
Let \(H\) = no horns (dominant) and \(h\) = horns (recessive); any horned animal must be \(hh\). Any hornless parent that produces a horned offspring must carry one recessive allele, so must be \(Hh\) (heterozygous).
By working through the pedigree, 4 animals can be identified as definitely heterozygous — hornless individuals that have produced at least one horned offspring, proving they carry the recessive allele.
✅ Answer: (C)
By working through the pedigree, 4 animals can be identified as definitely heterozygous — hornless individuals that have produced at least one horned offspring, proving they carry the recessive allele.
✅ Answer: (C)
▶️ Answer/Explanation
An ecosystem is defined as the combination of all living organisms (the biotic component) and their non-living physical environment (the abiotic component), interacting together as a system.
A decomposing log with the organisms inside it fits this definition perfectly — it has both a physical habitat and a community of organisms (fungi, bacteria, insects, etc.) interacting together; a food chain alone, or only the trees/burrows, are not complete ecosystems.
✅ Answer: (A)
A decomposing log with the organisms inside it fits this definition perfectly — it has both a physical habitat and a community of organisms (fungi, bacteria, insects, etc.) interacting together; a food chain alone, or only the trees/burrows, are not complete ecosystems.
✅ Answer: (A)
▶️ Answer/Explanation
Photosynthesis removes \(\text{CO}_2\) from the air and locks it in organic molecules, while respiration and combustion release \(\text{CO}_2\) back into the air — all three processes therefore change atmospheric \(\text{CO}_2\) levels.
Processes such as fossilisation or digestion do not directly exchange carbon dioxide with the atmosphere, so the correct combination is photosynthesis, respiration, and combustion — answer A.
✅ Answer: (A)
Processes such as fossilisation or digestion do not directly exchange carbon dioxide with the atmosphere, so the correct combination is photosynthesis, respiration, and combustion — answer A.
✅ Answer: (A)
▶️ Answer/Explanation
This is a simple distillation setup for purifying water from sea water: at position X (the heated flask), water evaporates (changes from liquid to gas), while at position Y (the condenser/collection flask), the water vapour condenses (changes from gas to liquid).
The salt remains behind in the flask because it does not evaporate; only pure water vapour travels to the collection vessel — matching row C which shows evaporation at X and condensation at Y.
✅ Answer: (C)
The salt remains behind in the flask because it does not evaporate; only pure water vapour travels to the collection vessel — matching row C which shows evaporation at X and condensation at Y.
✅ Answer: (C)
▶️ Answer/Explanation
A pipette is designed to deliver a precise, fixed volume of liquid and has a very narrow tip — it cannot collect or measure the volume of a gas produced in a reaction.
A gas syringe directly collects gas, a measuring cylinder (inverted over water) can collect gas by displacement, and a burette can also be used inverted — but a pipette has no mechanism to trap or measure gas volumes.
✅ Answer: (C)
A gas syringe directly collects gas, a measuring cylinder (inverted over water) can collect gas by displacement, and a burette can also be used inverted — but a pipette has no mechanism to trap or measure gas volumes.
✅ Answer: (C)
▶️ Answer/Explanation
Simple covalent molecules have no free electrons or ions in any state, so they do not conduct electricity — low electrical conductivity is a defining property of all simple covalent compounds.
They typically have low melting points (not high), are often volatile (not low volatility), and are generally not soluble in water (unless they can form hydrogen bonds or ionise); so the only universally correct property is low electrical conductivity.
✅ Answer: (A)
They typically have low melting points (not high), are often volatile (not low volatility), and are generally not soluble in water (unless they can form hydrogen bonds or ionise); so the only universally correct property is low electrical conductivity.
✅ Answer: (A)
▶️ Answer/Explanation
The ammonium ion has a charge of \(+1\) and the phosphate ion has a charge of \(-3\); to achieve electrical neutrality, 3 ammonium ions are needed for every 1 phosphate ion.
Therefore the formula is \((\text{NH}_4)_3\text{PO}_4\), giving a total charge of \(3(+1) + (-3) = 0\).
✅ Answer: (A)
Therefore the formula is \((\text{NH}_4)_3\text{PO}_4\), giving a total charge of \(3(+1) + (-3) = 0\).
✅ Answer: (A)
▶️ Answer/Explanation
Electrolysis is defined as the decomposition of an ionic compound (when molten or in solution) using an electric current — the compound is broken down into simpler substances at the electrodes.
Covalent compounds generally do not conduct electricity and cannot be electrolysed; only ionic compounds undergo electrolysis, and the products are always simpler than the starting compound.
✅ Answer: (D)
Covalent compounds generally do not conduct electricity and cannot be electrolysed; only ionic compounds undergo electrolysis, and the products are always simpler than the starting compound.
✅ Answer: (D)
▶️ Answer/Explanation
Burning (combustion) is a chemical change because new substances (\(\text{CO}_2\) and \(\text{H}_2\text{O}\)) are formed and the reaction is irreversible — the original match cannot be restored.
It is also an exothermic reaction because energy (heat and light) is released to the surroundings; therefore the correct row is B (chemical change, exothermic).
✅ Answer: (B)
It is also an exothermic reaction because energy (heat and light) is released to the surroundings; therefore the correct row is B (chemical change, exothermic).
✅ Answer: (B)
▶️ Answer/Explanation
At higher temperatures gas molecules move faster (higher kinetic energy), so they collide more frequently (statement 2 is correct); temperature does not cause molecules to move closer together, so statement 1 is wrong.
Higher temperature also means a greater proportion of molecules have kinetic energy exceeding the activation energy (statement 4 is correct); the activation energy itself does not change with temperature (statement 3 is wrong).
✅ Answer: (D)
Higher temperature also means a greater proportion of molecules have kinetic energy exceeding the activation energy (statement 4 is correct); the activation energy itself does not change with temperature (statement 3 is wrong).
✅ Answer: (D)
▶️ Answer/Explanation
Direct addition of sulfuric acid to barium carbonate (option A) would immediately form insoluble \(\text{BaSO}_4\) as a coating that prevents further reaction; instead, the barium carbonate must first be dissolved in dilute \(\text{HCl}\) to form soluble barium chloride solution.
The barium chloride solution is then mixed with aqueous sodium sulfate, causing precipitation: \(\text{BaCl}_2(aq) + \text{Na}_2\text{SO}_4(aq) \rightarrow \text{BaSO}_4(s) + 2\text{NaCl}(aq)\); barium carbonate is a solid (insoluble), so option C (aqueous barium carbonate) is incorrect — the solid must be reacted with acid, matching option D.
✅ Answer: (D)
The barium chloride solution is then mixed with aqueous sodium sulfate, causing precipitation: \(\text{BaCl}_2(aq) + \text{Na}_2\text{SO}_4(aq) \rightarrow \text{BaSO}_4(s) + 2\text{NaCl}(aq)\); barium carbonate is a solid (insoluble), so option C (aqueous barium carbonate) is incorrect — the solid must be reacted with acid, matching option D.
✅ Answer: (D)
▶️ Answer/Explanation
Electronic structure 2 corresponds to helium (He, atomic number 2), which is a noble gas — a non-metal. Structures 2,2 = beryllium (metal), 2,8,2 = magnesium (metal), and 2,8,8,2 = calcium (metal).
All of options B, C, and D have 2 electrons in their outermost shell (Group II), placing them firmly in the metallic block; only helium with just 2 electrons in one shell is a non-metal.
✅ Answer: (A)
All of options B, C, and D have 2 electrons in their outermost shell (Group II), placing them firmly in the metallic block; only helium with just 2 electrons in one shell is a non-metal.
✅ Answer: (A)
▶️ Answer/Explanation
Going down Group VII the halogens get darker in colour (F is pale yellow, Cl is yellow-green, Br is red-brown, I is grey/black) so tennessine, below astatine, would be expected to be very dark (black/solid).
Reactivity decreases down the group, so tennessine is less reactive than iodine and cannot displace iodide ions from potassium iodide solution — no reaction occurs, matching row B.
✅ Answer: (B)
Reactivity decreases down the group, so tennessine is less reactive than iodine and cannot displace iodide ions from potassium iodide solution — no reaction occurs, matching row B.
✅ Answer: (B)
▶️ Answer/Explanation
In the blast furnace, iron oxide (haematite, \(\text{Fe}_2\text{O}_3\)) is reduced to iron by carbon monoxide: \(\text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2\) — this makes statement C correct.
Aluminium ore is bauxite (not haematite); aluminium is extracted by electrolysis (not heating with carbon); and limestone removes acidic impurities (like silica), not basic ones.
✅ Answer: (C)
Aluminium ore is bauxite (not haematite); aluminium is extracted by electrolysis (not heating with carbon); and limestone removes acidic impurities (like silica), not basic ones.
✅ Answer: (C)
▶️ Answer/Explanation
Anhydrous copper(II) sulfate is white; when water is added it becomes hydrated copper(II) sulfate, which is blue — so the sentence reads: “water turns anhydrous copper(II) sulfate from white to blue“.
This is a standard test for the presence of water; the colour change from white to blue is a positive result, matching row D in the table.
✅ Answer: (D)
This is a standard test for the presence of water; the colour change from white to blue is a positive result, matching row D in the table.
✅ Answer: (D)
▶️ Answer/Explanation
Unsaturated hydrocarbons contain at least one carbon-to-carbon double bond; the simplest homologous series of unsaturated hydrocarbons is the alkenes, which have the general formula \(C_nH_{2n}\).
The formula \(C_nH_{2n+2}\) belongs to alkanes (saturated); \(C_nH_{2n}\) fits ethene (\(C_2H_4\)), propene (\(C_3H_6\)), etc., all of which contain one double bond and are unsaturated.
✅ Answer: (C)
The formula \(C_nH_{2n+2}\) belongs to alkanes (saturated); \(C_nH_{2n}\) fits ethene (\(C_2H_4\)), propene (\(C_3H_6\)), etc., all of which contain one double bond and are unsaturated.
✅ Answer: (C)
▶️ Answer/Explanation
Nylon is a condensation polymer formed when a diamine and a dicarboxylic acid react together, releasing water molecules and forming an amide linkage (–CONH–) between each pair of monomers.
Poly(ethene) is an addition polymer (no small molecule released); the two polymers use different monomers and have different types of linkages — only statement B is correct.
✅ Answer: (B)
Poly(ethene) is an addition polymer (no small molecule released); the two polymers use different monomers and have different types of linkages — only statement B is correct.
✅ Answer: (B)
▶️ Answer/Explanation
Density is defined as \(\rho = \dfrac{m}{V}\); the volume of the rectangular block is \(V = 25 \times 5 \times 8\) cm³ and the mass is 2700 g.
Therefore \(\rho = \dfrac{2700}{25 \times 5 \times 8}\) g/cm³, which corresponds to option D; numerically this equals \(\dfrac{2700}{1000} = 2.7\) g/cm³ (the density of aluminium).
✅ Answer: (D)
Therefore \(\rho = \dfrac{2700}{25 \times 5 \times 8}\) g/cm³, which corresponds to option D; numerically this equals \(\dfrac{2700}{1000} = 2.7\) g/cm³ (the density of aluminium).
✅ Answer: (D)
▶️ Answer/Explanation
Hooke’s Law states that extension is proportional to force up to the limit of proportionality; from the table, equal increases in force produce equal increases in extension up to a certain point, after which the extension per unit force becomes larger (non-proportional).
By examining where the equal-increment pattern breaks down in the table, the limit of proportionality falls between the 31 cm and 35 cm readings — the spring is still obeying Hooke’s Law at 31 cm but not at 35 cm.
✅ Answer: (B)
By examining where the equal-increment pattern breaks down in the table, the limit of proportionality falls between the 31 cm and 35 cm readings — the spring is still obeying Hooke’s Law at 31 cm but not at 35 cm.
✅ Answer: (B)
▶️ Answer/Explanation
Applying the principle of moments: clockwise moment = anticlockwise moment, so \(250 \times 1.6 = W_2 \times 1.2\).
Solving: \(W_2 = \dfrac{250 \times 1.6}{1.2} = \dfrac{400}{1.2} \approx 333 \approx 330\) N, which corresponds to option C.
✅ Answer: (C)
Solving: \(W_2 = \dfrac{250 \times 1.6}{1.2} = \dfrac{400}{1.2} \approx 333 \approx 330\) N, which corresponds to option C.
✅ Answer: (C)
▶️ Answer/Explanation
Natural gas is a fossil fuel formed from ancient organisms that stored solar energy; solar panels directly convert sunlight; and wind is driven by temperature differences caused by the Sun — all three are solely solar-derived.
Option A includes geothermal (Earth’s internal heat, not solar); option B includes tidal (gravitational energy from the Moon/Sun, not solely solar); option D includes nuclear (nuclear binding energy, not solar).
✅ Answer: (C)
Option A includes geothermal (Earth’s internal heat, not solar); option B includes tidal (gravitational energy from the Moon/Sun, not solely solar); option D includes nuclear (nuclear binding energy, not solar).
✅ Answer: (C)
▶️ Answer/Explanation
The ability to flow (fluidity) is a property shared by both liquids and gases — their particles can move past one another; solids have particles held in fixed positions in a regular lattice, so they cannot flow.
Since substance X does not flow, it must be a solid; it cannot be a gas or liquid because both of those states are defined by their ability to flow and take the shape of their container.
✅ Answer: (D)
Since substance X does not flow, it must be a solid; it cannot be a gas or liquid because both of those states are defined by their ability to flow and take the shape of their container.
✅ Answer: (D)
▶️ Answer/Explanation
When light travels from a denser medium (glass) into a less dense medium (air), it refracts away from the normal — the angle of refraction in air is greater than the angle of incidence in glass.
At the same time, the speed of light increases because air is optically less dense than glass (light travels at approximately \(2 \times 10^8\) m/s in glass but \(3 \times 10^8\) m/s in air) — this matches row B.
✅ Answer: (B)
At the same time, the speed of light increases because air is optically less dense than glass (light travels at approximately \(2 \times 10^8\) m/s in glass but \(3 \times 10^8\) m/s in air) — this matches row B.
✅ Answer: (B)
▶️ Answer/Explanation
All electromagnetic waves travel at the same speed in a vacuum, \(c = 3 \times 10^8\) m/s — speed does not vary across the spectrum in a vacuum.
In the electromagnetic spectrum, gamma rays have the highest frequency (and shortest wavelength), while microwaves have a much lower frequency — so gamma rays have greater frequency than microwaves but both travel at the same speed.
✅ Answer: (B)
In the electromagnetic spectrum, gamma rays have the highest frequency (and shortest wavelength), while microwaves have a much lower frequency — so gamma rays have greater frequency than microwaves but both travel at the same speed.
✅ Answer: (B)
▶️ Answer/Explanation
An electromagnet needs to be switched on and off rapidly; soft iron is ideal because it is easily magnetised when a current flows and loses its magnetism quickly when the current is switched off.
Steel would retain its magnetism even after the current stops (making it a permanent magnet), which is undesirable for an electromagnet — so the core is soft iron because it is easy to magnetise (and demagnetise).
✅ Answer: (A)
Steel would retain its magnetism even after the current stops (making it a permanent magnet), which is undesirable for an electromagnet — so the core is soft iron because it is easy to magnetise (and demagnetise).
✅ Answer: (A)
▶️ Answer/Explanation
Using \(R \propto \dfrac{L}{A}\): doubling the length doubles resistance (×2), while doubling the cross-sectional area halves resistance (×½) — the combined effect is \(\times 2 \times \frac{1}{2} = \times 1\), so the resistance stays the same.
Therefore the second wire has the same resistance as the first: \(8.0\) Ω.
✅ Answer: (B)
Therefore the second wire has the same resistance as the first: \(8.0\) Ω.
✅ Answer: (B)
▶️ Answer/Explanation
In a parallel circuit, the current from the cell (\(I_1\)) splits at the junction and flows through each branch separately (\(I_2\) and \(I_3\)); by conservation of charge, the total current must equal the sum of the branch currents.
Therefore \(I_1 = I_2 + I_3\); this is Kirchhoff’s current law — charge is neither created nor destroyed at a junction.
✅ Answer: (D)
Therefore \(I_1 = I_2 + I_3\); this is Kirchhoff’s current law — charge is neither created nor destroyed at a junction.
✅ Answer: (D)
▶️ Answer/Explanation
A fuse is a safety device that melts and breaks the circuit when the current exceeds its rated value; a 13 A fuse will only blow at currents above 13 A, so if a fault causes a current of, say, 5 A to flow, the 13 A fuse will NOT blow.
This means the wires carry a dangerously high current for which they are not rated — they can overheat, potentially causing a fire; the brightness and voltage of the lamp are unaffected by the fuse rating during normal operation.
✅ Answer: (C)
This means the wires carry a dangerously high current for which they are not rated — they can overheat, potentially causing a fire; the brightness and voltage of the lamp are unaffected by the fuse rating during normal operation.
✅ Answer: (C)
▶️ Answer/Explanation
For a 100% efficient transformer, input power = output power: \(V_p I_p = V_s I_s\), so \(100 \times 10 = 20 \times I_s\).
Solving: \(I_s = \dfrac{100 \times 10}{20} = \dfrac{1000}{20} = 50\) A; the output voltage is lower (step-down transformer), so the output current must be proportionally higher to conserve power.
✅ Answer: (C)
Solving: \(I_s = \dfrac{100 \times 10}{20} = \dfrac{1000}{20} = 50\) A; the output voltage is lower (step-down transformer), so the output current must be proportionally higher to conserve power.
✅ Answer: (C)
▶️ Answer/Explanation
In the first decay \(({}_{92}^{238}\text{U} \rightarrow {}_{90}^{234}\text{Th})\): mass number decreases by 4 and atomic number decreases by 2 — this is characteristic of alpha (\(\alpha\)) decay (emission of \({}_{2}^{4}\text{He}\)).
In the second decay \(({}_{90}^{234}\text{Th} \rightarrow {}_{91}^{234}\text{Pa})\): mass number stays at 234 but atomic number increases by 1 — this is characteristic of beta (\(\beta^-\)) decay (a neutron converts to a proton, emitting an electron).
✅ Answer: (A)
In the second decay \(({}_{90}^{234}\text{Th} \rightarrow {}_{91}^{234}\text{Pa})\): mass number stays at 234 but atomic number increases by 1 — this is characteristic of beta (\(\beta^-\)) decay (a neutron converts to a proton, emitting an electron).
✅ Answer: (A)