▶️ Answer/Explanation
Sensitivity is the characteristic that allows an organism to detect and respond to stimuli in its environment.
The shoot detects gravity and light and grows upwards (positive phototropism), while the root grows downwards (positive gravitropism) — both responses are driven by sensitivity.
✅ Answer: (D)
The shoot detects gravity and light and grows upwards (positive phototropism), while the root grows downwards (positive gravitropism) — both responses are driven by sensitivity.
✅ Answer: (D)
▶️ Answer/Explanation
Diffusion is the net movement of molecules from a region of higher concentration to a region of lower concentration.
This movement is described as moving down the concentration gradient — no energy (ATP) is required for this process.
✅ Answer: (A)
This movement is described as moving down the concentration gradient — no energy (ATP) is required for this process.
✅ Answer: (A)
▶️ Answer/Explanation
Glycogen is a polysaccharide — a large carbohydrate molecule made from many glucose monomer units joined together by glycosidic bonds.
It acts as the main energy storage carbohydrate in animal cells, particularly in the liver and muscle tissue.
✅ Answer: (C)
It acts as the main energy storage carbohydrate in animal cells, particularly in the liver and muscle tissue.
✅ Answer: (C)
▶️ Answer/Explanation
From the graph, enzyme X has an optimum around pH 7–8 and enzyme Y has an optimum around pH 5; both enzymes show measurable activity at pH 5.
Statements A, C, and D are incorrect because the graph shows both enzymes have some activity at pH 4, only enzyme Y is active at pH 10, and both enzymes are active at pH 3 respectively.
✅ Answer: (B)
Statements A, C, and D are incorrect because the graph shows both enzymes have some activity at pH 4, only enzyme Y is active at pH 10, and both enzymes are active at pH 3 respectively.
✅ Answer: (B)
▶️ Answer/Explanation
The full word equation for photosynthesis is: \(\text{carbon dioxide} + \text{water} \xrightarrow{\text{light, chlorophyll}} \text{glucose} + \text{oxygen}\).
Water is a reactant (not a product) in photosynthesis; the oxygen released as a by-product comes from the splitting of water molecules during the light-dependent stage.
✅ Answer: (D)
Water is a reactant (not a product) in photosynthesis; the oxygen released as a by-product comes from the splitting of water molecules during the light-dependent stage.
✅ Answer: (D)
▶️ Answer/Explanation
Calcium is an essential mineral needed for the development and maintenance of strong bones and teeth.
Iron is needed to produce haemoglobin in red blood cells, which is the pigment responsible for carrying oxygen around the body.
✅ Answer: (C)
Iron is needed to produce haemoglobin in red blood cells, which is the pigment responsible for carrying oxygen around the body.
✅ Answer: (C)
▶️ Answer/Explanation
The aorta is the largest artery in the body, carrying oxygenated blood away from the left ventricle to the rest of the body.
Blood flow in the aorta is directed away from the heart, making it an artery carrying blood from the heart to the body.
✅ Answer: (A)
Blood flow in the aorta is directed away from the heart, making it an artery carrying blood from the heart to the body.
✅ Answer: (A)
▶️ Answer/Explanation
Limewater (calcium hydroxide solution) is the standard test for carbon dioxide — when \(\text{CO}_2\) is bubbled through it, a white precipitate of calcium carbonate forms, turning the solution milky/cloudy.
The reaction is: \(\text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{H}_2\text{O}\).
✅ Answer: (D)
The reaction is: \(\text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{H}_2\text{O}\).
✅ Answer: (D)
▶️ Answer/Explanation
In a reflex arc, the signal travels from receptor → sensory neurone (X) → relay neurone (Y) in the spinal cord → motor neurone (Z) → effector.
The sensory neurone carries impulses from receptor to CNS, the relay neurone connects within the CNS, and the motor neurone carries impulses from CNS to the effector (muscle or gland).
✅ Answer: (B)
The sensory neurone carries impulses from receptor to CNS, the relay neurone connects within the CNS, and the motor neurone carries impulses from CNS to the effector (muscle or gland).
✅ Answer: (B)
▶️ Answer/Explanation
Asexual reproduction does NOT involve gametes (statement 1 is false) — it uses mitosis only, so no fertilisation occurs.
Statements 2 and 3 are correct: asexual reproduction requires only one parent and produces offspring that are genetically identical (clones) to the parent.
✅ Answer: (D)
Statements 2 and 3 are correct: asexual reproduction requires only one parent and produces offspring that are genetically identical (clones) to the parent.
✅ Answer: (D)
▶️ Answer/Explanation
A dominant allele is always expressed in the phenotype whenever it is present, regardless of whether the organism is homozygous or heterozygous for that allele.
In contrast, a recessive allele is only expressed when two copies are present (homozygous recessive); heterozygous and homozygous describe the genotype, not the dominance of an allele.
✅ Answer: (A)
In contrast, a recessive allele is only expressed when two copies are present (homozygous recessive); heterozygous and homozygous describe the genotype, not the dominance of an allele.
✅ Answer: (A)
▶️ Answer/Explanation
Carnivores are animals that obtain their nutrition by eating other animals; in the food web, kingfishers, perch, and water beetles all feed on other animals (not plants).
Tadpoles and freshwater shrimp feed on plants/algae making them herbivores, not carnivores.
✅ Answer: (A)
Tadpoles and freshwater shrimp feed on plants/algae making them herbivores, not carnivores.
✅ Answer: (A)
▶️ Answer/Explanation
Transpiration is the evaporation and movement of water through plants and out via the stomata — it is part of the water cycle, not the carbon cycle.
Combustion, fossilisation, and photosynthesis all involve the movement of carbon between the atmosphere, living organisms, and the Earth, so they are all parts of the carbon cycle.
✅ Answer: (C)
Combustion, fossilisation, and photosynthesis all involve the movement of carbon between the atmosphere, living organisms, and the Earth, so they are all parts of the carbon cycle.
✅ Answer: (C)
▶️ Answer/Explanation
Combustion of hydrocarbons is a chemical change because new substances (\(\text{CO}_2\) and \(\text{H}_2\text{O}\)) are formed and the reaction is not easily reversible.
Options B, C, and D are all physical changes — no new substances are formed, and the changes are reversible (e.g. freezing water is the reverse of melting).
✅ Answer: (A)
Options B, C, and D are all physical changes — no new substances are formed, and the changes are reversible (e.g. freezing water is the reverse of melting).
✅ Answer: (A)
▶️ Answer/Explanation
For \( {}_{12}^{25}\text{Mg} \): the proton number (atomic number) is 12, so the nucleus contains 12 protons; the nucleon number (mass number) is 25, so the number of neutrons \( = 25 – 12 = 13 \).
The nucleus therefore contains 12 protons and 13 neutrons (electrons are outside the nucleus and are not counted here).
✅ Answer: (B)
The nucleus therefore contains 12 protons and 13 neutrons (electrons are outside the nucleus and are not counted here).
✅ Answer: (B)
▶️ Answer/Explanation
Ammonia (\(\text{NH}_3\)) has a nitrogen atom with 5 outer electrons forming 3 single covalent bonds with 3 hydrogen atoms, leaving 1 lone pair on nitrogen.
The correct dot-and-cross diagram shows nitrogen sharing one electron with each of the three hydrogen atoms, with a lone pair remaining on nitrogen — this is option C.
✅ Answer: (C)
The correct dot-and-cross diagram shows nitrogen sharing one electron with each of the three hydrogen atoms, with a lone pair remaining on nitrogen — this is option C.
✅ Answer: (C)
▶️ Answer/Explanation
To find the molecular formula, count each type of atom in the displayed structure: 4 carbon atoms, 6 hydrogen atoms, and 3 oxygen atoms.
This gives the molecular formula \(\text{C}_4\text{H}_6\text{O}_3\), which corresponds to option C.
✅ Answer: (C)
This gives the molecular formula \(\text{C}_4\text{H}_6\text{O}_3\), which corresponds to option C.
✅ Answer: (C)
▶️ Answer/Explanation
During electrolysis of concentrated sodium chloride solution: hydrogen (\(\text{H}_2\)) is produced at the cathode — it burns with a squeaky pop when a lighted splint is applied.
Chlorine (\(\text{Cl}_2\)) is produced at the anode — it bleaches damp litmus paper, turning it white; this matches option C.
✅ Answer: (C)
Chlorine (\(\text{Cl}_2\)) is produced at the anode — it bleaches damp litmus paper, turning it white; this matches option C.
✅ Answer: (C)
▶️ Answer/Explanation
The test-tube becomes warm, meaning heat energy is being released to the surroundings — this is the definition of an exothermic reaction.
Endothermic reactions absorb heat energy and would cause the temperature to fall; combustion requires oxygen and is a specific type of exothermic reaction, but the question asks what explains the warming.
✅ Answer: (D)
Endothermic reactions absorb heat energy and would cause the temperature to fall; combustion requires oxygen and is a specific type of exothermic reaction, but the question asks what explains the warming.
✅ Answer: (D)
▶️ Answer/Explanation
Oxidation is defined as the gain of oxygen; during rusting, iron reacts with oxygen (and water) to form hydrated iron(III) oxide (\(\text{Fe}_2\text{O}_3 \cdot \text{H}_2\text{O}\)).
Since iron gains oxygen in this process, rusting is correctly classified as an oxidation reaction; the fact that iron is a transition element or reactive metal does not explain why the reaction is oxidation.
✅ Answer: (A)
Since iron gains oxygen in this process, rusting is correctly classified as an oxidation reaction; the fact that iron is a transition element or reactive metal does not explain why the reaction is oxidation.
✅ Answer: (A)
▶️ Answer/Explanation
Ammonia is a basic gas that reacts with acids; concentrated hydrochloric acid reacts with ammonia to produce dense white fumes of ammonium chloride: \(\text{NH}_3 + \text{HCl} \rightarrow \text{NH}_4\text{Cl}\).
This white smoke test is used to confirm the presence of ammonia gas; other options in the table (like sodium hydroxide solution or water) do not produce this characteristic white smoke.
✅ Answer: (B)
This white smoke test is used to confirm the presence of ammonia gas; other options in the table (like sodium hydroxide solution or water) do not produce this characteristic white smoke.
✅ Answer: (B)
▶️ Answer/Explanation
Halogens exist as diatomic molecules (e.g. \(\text{Cl}_2\), \(\text{Br}_2\)), so gap 1 is “diatomic”.
Going down Group VII: fluorine is pale yellow, chlorine is yellow-green, bromine is orange-brown, and iodine is grey/black — the colour gets darker, so gap 2 is “darker”.
✅ Answer: (A)
Going down Group VII: fluorine is pale yellow, chlorine is yellow-green, bromine is orange-brown, and iodine is grey/black — the colour gets darker, so gap 2 is “darker”.
✅ Answer: (A)
▶️ Answer/Explanation
Element X acts as a catalyst — it increases the rate of reaction but is chemically unchanged at the end; this is a key property of transition elements (e.g. iron, nickel, platinum).
Transition elements are located in the central d-block region (between Groups II and III) of the Periodic Table, which corresponds to option D.
✅ Answer: (D)
Transition elements are located in the central d-block region (between Groups II and III) of the Periodic Table, which corresponds to option D.
✅ Answer: (D)
▶️ Answer/Explanation
Aluminium is extracted from bauxite (its ore), not hematite — hematite is the ore of iron; bauxite contains aluminium oxide (\(\text{Al}_2\text{O}_3\)).
Because aluminium is above carbon in the reactivity series, carbon cannot reduce it, so electrolysis of molten aluminium oxide is used instead.
✅ Answer: (B)
Because aluminium is above carbon in the reactivity series, carbon cannot reduce it, so electrolysis of molten aluminium oxide is used instead.
✅ Answer: (B)
▶️ Answer/Explanation
When water is added to white anhydrous copper(II) sulfate, it turns blue (forming hydrated copper(II) sulfate, \(\text{CuSO}_4 \cdot 5\text{H}_2\text{O}\)).
When water is added to blue anhydrous cobalt(II) chloride, it turns pink (forming hydrated cobalt(II) chloride); this matches option C.
✅ Answer: (C)
When water is added to blue anhydrous cobalt(II) chloride, it turns pink (forming hydrated cobalt(II) chloride); this matches option C.
✅ Answer: (C)
▶️ Answer/Explanation
Natural gas is mainly composed of methane, \(\text{CH}_4\).
Methane is the simplest hydrocarbon, containing only one carbon atom.
That single carbon atom forms four single covalent bonds, one to each of four hydrogen atoms.
Structure A shows this arrangement — one central carbon singly bonded to four hydrogens, with no carbon–carbon bonds.
✅ Answer: (A)
Methane is the simplest hydrocarbon, containing only one carbon atom.
That single carbon atom forms four single covalent bonds, one to each of four hydrogen atoms.
Structure A shows this arrangement — one central carbon singly bonded to four hydrogens, with no carbon–carbon bonds.
✅ Answer: (A)
▶️ Answer/Explanation
Ethene, \(\text{C}_2\text{H}_4\), contains a reactive carbon–carbon double bond.
This double bond allows ethene to undergo addition reactions.
When steam is added across the double bond in the presence of an acid catalyst, water is incorporated into the molecule.
This addition of steam converts ethene directly into ethanol, \(\text{C}_2\text{H}_5\text{OH}\).
✅ Answer: (D)
This double bond allows ethene to undergo addition reactions.
When steam is added across the double bond in the presence of an acid catalyst, water is incorporated into the molecule.
This addition of steam converts ethene directly into ethanol, \(\text{C}_2\text{H}_5\text{OH}\).
✅ Answer: (D)
▶️ Answer/Explanation
Average speed is calculated using \(\text{average speed} = \dfrac{\text{total distance}}{\text{total time}}\).
The total distance travelled is \(100 + 300 = 400\text{ m}\).
The total time taken is \(10 + 15 = 25\text{ s}\).
So, average speed \(= \dfrac{400}{25} = 16\text{ m/s}\).
✅ Answer: (D)
The total distance travelled is \(100 + 300 = 400\text{ m}\).
The total time taken is \(10 + 15 = 25\text{ s}\).
So, average speed \(= \dfrac{400}{25} = 16\text{ m/s}\).
✅ Answer: (D)
▶️ Answer/Explanation
A train moving at constant speed has zero acceleration, so by Newton’s first law the resultant force on it must be zero.
Combining the two forces shown in the diagram with the air resistance force must therefore give a net force of \(0\text{ N}\).
Working through \(F_{\text{forward}} – F_{\text{other}} – F_{\text{air resistance}} = 0\) using the magnitudes in the diagram gives an air resistance force of \(40\,000\text{ N}\).
Since this force opposes the train’s motion, it must act backwards.
✅ Answer: (A)
Combining the two forces shown in the diagram with the air resistance force must therefore give a net force of \(0\text{ N}\).
Working through \(F_{\text{forward}} – F_{\text{other}} – F_{\text{air resistance}} = 0\) using the magnitudes in the diagram gives an air resistance force of \(40\,000\text{ N}\).
Since this force opposes the train’s motion, it must act backwards.
✅ Answer: (A)
▶️ Answer/Explanation
Geothermal, nuclear and wind resources all generate electricity by using steam or moving air to spin a turbine connected to a generator.
Solar cells work differently: they convert light energy directly into electrical energy using the photovoltaic effect.
No rotating turbine is involved at any stage of this process.
✅ Answer: (C)
Solar cells work differently: they convert light energy directly into electrical energy using the photovoltaic effect.
No rotating turbine is involved at any stage of this process.
✅ Answer: (C)
▶️ Answer/Explanation
A liquid expands as its temperature increases and contracts as its temperature decreases.
In a liquid-in-glass thermometer, this change in volume moves the liquid up or down a narrow tube.
The position of the liquid against a calibrated scale therefore indicates the temperature.
✅ Answer: (D)
In a liquid-in-glass thermometer, this change in volume moves the liquid up or down a narrow tube.
The position of the liquid against a calibrated scale therefore indicates the temperature.
✅ Answer: (D)
▶️ Answer/Explanation
Amplitude is the maximum displacement of the wave from its rest (undisturbed) position.
As the wave passes, the boat rises and falls, moving from its lowest point to its highest point.
The vertical distance between these two points is equal to twice the amplitude, \(2A\).
Dividing this single measurement by 2 directly gives the amplitude of the wave.
✅ Answer: (D)
As the wave passes, the boat rises and falls, moving from its lowest point to its highest point.
The vertical distance between these two points is equal to twice the amplitude, \(2A\).
Dividing this single measurement by 2 directly gives the amplitude of the wave.
✅ Answer: (D)
▶️ Answer/Explanation
The angle of refraction must always be measured between the refracted ray and the normal, which is perpendicular to the boundary.
In this diagram, angle Q is marked between the ray and the boundary surface itself, not the normal.
Since the normal is at 90° to the surface, the true angle from the normal is \(90° – Q\).
✅ Answer: (D)
In this diagram, angle Q is marked between the ray and the boundary surface itself, not the normal.
Since the normal is at 90° to the surface, the true angle from the normal is \(90° – Q\).
✅ Answer: (D)
▶️ Answer/Explanation
An echo means the sound must travel from the student to the wall and then reflect back, a total distance of \(2 \times 100 = 200\text{ m}\).
Using \(\text{time} = \dfrac{\text{distance}}{\text{speed}}\), the time taken is \(\dfrac{200}{330}\).
This works out to approximately \(0.61\text{ s}\).
✅ Answer: (B)
Using \(\text{time} = \dfrac{\text{distance}}{\text{speed}}\), the time taken is \(\dfrac{200}{330}\).
This works out to approximately \(0.61\text{ s}\).
✅ Answer: (B)
▶️ Answer/Explanation
Two charged rods only repel each other if they carry the same type of charge, either both positive or both negative.
Charging by friction works by transferring electrons from one material to another, never by transferring positive charge.
The material that loses electrons becomes positively charged, while the material that gains electrons becomes negatively charged.
Row A is the only description in which both rods end up with the same sign of charge, consistent with a repulsive force.
✅ Answer: (A)
Charging by friction works by transferring electrons from one material to another, never by transferring positive charge.
The material that loses electrons becomes positively charged, while the material that gains electrons becomes negatively charged.
Row A is the only description in which both rods end up with the same sign of charge, consistent with a repulsive force.
✅ Answer: (A)
▶️ Answer/Explanation
Resistance is calculated using \(R = \dfrac{V}{I}\).
The potential difference is 12 V and the current is 4.0 A.
So, \(R = \dfrac{12}{4.0} = 3.0\ \Omega\).
✅ Answer: (B)
The potential difference is 12 V and the current is 4.0 A.
So, \(R = \dfrac{12}{4.0} = 3.0\ \Omega\).
✅ Answer: (B)
▶️ Answer/Explanation
A fuse must have a rating just above the normal operating current so it does not blow during ordinary use.
The 1 A and 5 A fuses are both below 6.0 A, so they would blow even under normal conditions.
The 20 A fuse is far too high and would allow a dangerous fault current to flow without breaking the circuit.
The 8 A fuse sits just above the 6.0 A normal current, allowing safe operation while still protecting against a fault.
✅ Answer: (C)
The 1 A and 5 A fuses are both below 6.0 A, so they would blow even under normal conditions.
The 20 A fuse is far too high and would allow a dangerous fault current to flow without breaking the circuit.
The 8 A fuse sits just above the 6.0 A normal current, allowing safe operation while still protecting against a fault.
✅ Answer: (C)
▶️ Answer/Explanation
The magnetic field around a straight current-carrying wire forms concentric circles centred on the wire.
The direction of these circles is found using the right-hand grip rule.
Since the current flows into the page, the field circles run clockwise when viewed from the reader’s side of the page.
Diagram C is the only one showing concentric circles in this clockwise direction.
✅ Answer: (C)
The direction of these circles is found using the right-hand grip rule.
Since the current flows into the page, the field circles run clockwise when viewed from the reader’s side of the page.
Diagram C is the only one showing concentric circles in this clockwise direction.
✅ Answer: (C)
▶️ Answer/Explanation
The count rate halves each time one half-life passes.
Following the sequence: \(1280 \to 640 \to 320 \to 160 \to 80\), the count rate halves 4 times.
These 4 half-lives take place over the given 20 minutes.
So, one half-life \(= \dfrac{20}{4} = 5.0\) minutes.
✅ Answer: (B)
Following the sequence: \(1280 \to 640 \to 320 \to 160 \to 80\), the count rate halves 4 times.
These 4 half-lives take place over the given 20 minutes.
So, one half-life \(= \dfrac{20}{4} = 5.0\) minutes.
✅ Answer: (B)
▶️ Answer/Explanation
An alpha (α)-particle is a helium nucleus, made up of 2 protons and 2 neutrons.
When a nucleus emits an alpha particle, it loses these 2 protons, so the proton number decreases by 2.
It also loses a total of 4 nucleons (2 protons + 2 neutrons), so the nucleon number decreases by 4.
✅ Answer: (A)
When a nucleus emits an alpha particle, it loses these 2 protons, so the proton number decreases by 2.
It also loses a total of 4 nucleons (2 protons + 2 neutrons), so the nucleon number decreases by 4.
✅ Answer: (A)