▶️ Answer/Explanation
Respiration is the process by which cells break down nutrient molecules, such as glucose, to release energy for metabolism.
Excretion is removal of waste, nutrition is taking in materials, and reproduction is making more organisms — none involve energy release from breakdown of nutrients.
✅ Answer: (D)
Excretion is removal of waste, nutrition is taking in materials, and reproduction is making more organisms — none involve energy release from breakdown of nutrients.
✅ Answer: (D)
▶️ Answer/Explanation
Magnification compares how much larger an image appears than the real object.
It is defined as \( \text{magnification} = \dfrac{\text{image size}}{\text{actual size}} \), a ratio with no units.
✅ Answer: (C)
It is defined as \( \text{magnification} = \dfrac{\text{image size}}{\text{actual size}} \), a ratio with no units.
✅ Answer: (C)
▶️ Answer/Explanation
Fats (lipids) are built from one glycerol molecule joined to three fatty acid molecules.
Glycogen and starch are polysaccharides made of glucose units, and proteins are made of amino acids, so none contain glycerol.
✅ Answer: (A)
Glycogen and starch are polysaccharides made of glucose units, and proteins are made of amino acids, so none contain glycerol.
✅ Answer: (A)
▶️ Answer/Explanation
Enzymes are proteins, built from amino acids.
Amino acids contain carbon, hydrogen, oxygen and nitrogen, so all three listed elements (carbon, nitrogen, oxygen) are present.
✅ Answer: (A)
Amino acids contain carbon, hydrogen, oxygen and nitrogen, so all three listed elements (carbon, nitrogen, oxygen) are present.
✅ Answer: (A)
▶️ Answer/Explanation
Photosynthesis uses carbon dioxide and water as raw materials, with light energy absorbed by chlorophyll.
The products are glucose and oxygen: \( 6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2 \).
✅ Answer: (B)
The products are glucose and oxygen: \( 6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2 \).
✅ Answer: (B)
▶️ Answer/Explanation
Canine teeth are pointed and cone-shaped, used for gripping and tearing food.
Option D shows this pointed shape, distinct from the flat incisors, wide premolars and molars in the other options.
✅ Answer: (D)
Option D shows this pointed shape, distinct from the flat incisors, wide premolars and molars in the other options.
✅ Answer: (D)
▶️ Answer/Explanation
Roots have a central xylem core, stems have vascular bundles arranged around the periphery, and leaf mid-ribs have a single central bundle.
Matching each section shape to these known arrangements gives root = R, stem = P, leaf = Q.
✅ Answer: (C)
Matching each section shape to these known arrangements gives root = R, stem = P, leaf = Q.
✅ Answer: (C)
▶️ Answer/Explanation
Flask X (with live respiring larvae) releases extra carbon dioxide, turning the indicator yellow.
Flask Y (control, no larvae) has indicator at atmospheric carbon dioxide level, so it stays orange.
✅ Answer: (B)
Flask Y (control, no larvae) has indicator at atmospheric carbon dioxide level, so it stays orange.
✅ Answer: (B)
▶️ Answer/Explanation
Gravitropism is a growth response to gravity.
Since the root grows towards (in the direction of) gravity, this is a positive gravitropic response.
✅ Answer: (C)
Since the root grows towards (in the direction of) gravity, this is a positive gravitropic response.
✅ Answer: (C)
▶️ Answer/Explanation
The graph gives no information about condom promotion, so statement 1 cannot be concluded.
Deaths from AIDS fall after anti-HIV drugs are introduced, supporting statement 2, while deaths actually peak later than 1995, so statement 3 is false.
✅ Answer: (D)
Deaths from AIDS fall after anti-HIV drugs are introduced, supporting statement 2, while deaths actually peak later than 1995, so statement 3 is false.
✅ Answer: (D)
▶️ Answer/Explanation
Human sex is determined by one pair of chromosomes.
Males have one X chromosome and one Y chromosome (XY), while females have two X chromosomes (XX).
✅ Answer: (C)
Males have one X chromosome and one Y chromosome (XY), while females have two X chromosomes (XX).
✅ Answer: (C)
▶️ Answer/Explanation
Decomposers, such as bacteria and fungi, feed on dead organisms and organic waste.
Carnivores, herbivores and producers obtain energy from living prey, plants, or sunlight respectively, not dead matter.
✅ Answer: (B)
Carnivores, herbivores and producers obtain energy from living prey, plants, or sunlight respectively, not dead matter.
✅ Answer: (B)
▶️ Answer/Explanation
Tree roots normally bind and stabilise soil, and their canopy reduces the impact of rain.
Removing trees exposes soil to wind and rain, leading to erosion and loss of fertile topsoil.
✅ Answer: (B)
Removing trees exposes soil to wind and rain, leading to erosion and loss of fertile topsoil.
✅ Answer: (B)
▶️ Answer/Explanation
Gases are easily compressed due to widely spaced particles, while solids are not, so compressibility distinguishes them.
Solids and gases also have very different melting points, but flammability is a chemical property unrelated to physical state.
✅ Answer: (A)
Solids and gases also have very different melting points, but flammability is a chemical property unrelated to physical state.
✅ Answer: (A)
▶️ Answer/Explanation
The subscript 9 is the proton (atomic) number, giving 9 protons.
A neutral atom has equal numbers of protons and electrons, so it contains 9 electrons.
✅ Answer: (A)
A neutral atom has equal numbers of protons and electrons, so it contains 9 electrons.
✅ Answer: (A)
▶️ Answer/Explanation
A balanced equation must have equal numbers of each atom on both sides.
\( 2H_2 + O_2 \rightarrow 2H_2O \) gives 4 hydrogen atoms and 2 oxygen atoms on each side, so it is correctly balanced.
✅ Answer: (D)
\( 2H_2 + O_2 \rightarrow 2H_2O \) gives 4 hydrogen atoms and 2 oxygen atoms on each side, so it is correctly balanced.
✅ Answer: (D)
▶️ Answer/Explanation
Sodium chloride is an ionic compound that can be split into its elements by electrolysis.
Passing an electric current through molten sodium chloride produces sodium at the cathode and chlorine at the anode.
✅ Answer: (D)
Passing an electric current through molten sodium chloride produces sodium at the cathode and chlorine at the anode.
✅ Answer: (D)
▶️ Answer/Explanation
A temperature increase means an exothermic reaction, so the largest increase (Y, +9 °C) is most exothermic.
A temperature decrease means endothermic; the smallest decrease (Z, −4 °C) is the least endothermic.
✅ Answer: (D)
A temperature decrease means endothermic; the smallest decrease (Z, −4 °C) is the least endothermic.
✅ Answer: (D)
▶️ Answer/Explanation
Carbonates react with dilute acids following the general pattern: carbonate + acid → salt + water + carbon dioxide.
Here, \( CuCO_3 + 2HCl \rightarrow CuCl_2 + H_2O + CO_2 \), so carbon dioxide gas is released.
✅ Answer: (A)
Here, \( CuCO_3 + 2HCl \rightarrow CuCl_2 + H_2O + CO_2 \), so carbon dioxide gas is released.
✅ Answer: (A)
▶️ Answer/Explanation
Halogens are all diatomic, non-metallic, and darken in colour down the group (chlorine pale green, iodine dark grey/purple).
However, their physical state changes down the group — chlorine is a gas, bromine a liquid, and iodine a solid — so not all are gases at room temperature.
✅ Answer: (C)
However, their physical state changes down the group — chlorine is a gas, bromine a liquid, and iodine a solid — so not all are gases at room temperature.
✅ Answer: (C)
▶️ Answer/Explanation
Noble gases are inert and do not react with the hot metal filament.
Argon is the noble gas commonly used to fill filament lamps, stopping the filament from burning away.
✅ Answer: (A)
Argon is the noble gas commonly used to fill filament lamps, stopping the filament from burning away.
✅ Answer: (A)
▶️ Answer/Explanation
Alloys are mixtures of metals, not chemically bonded compounds, since the elements are not combined in fixed proportions.
Because all alloys retain metallic bonding with delocalised electrons, all alloys conduct electricity.
✅ Answer: (C)
Because all alloys retain metallic bonding with delocalised electrons, all alloys conduct electricity.
✅ Answer: (C)
▶️ Answer/Explanation
Carbon can displace a metal from its oxide only if carbon is more reactive than that metal.
This displacement reduces the metal oxide to the free metal, releasing carbon dioxide.
✅ Answer: (B)
This displacement reduces the metal oxide to the free metal, releasing carbon dioxide.
✅ Answer: (B)
▶️ Answer/Explanation
White anhydrous copper(II) sulfate turns blue when water is added, as hydrated copper sulfate forms.
Blue cobalt(II) chloride paper turns pink in the presence of water.
✅ Answer: (B)
Blue cobalt(II) chloride paper turns pink in the presence of water.
✅ Answer: (B)
▶️ Answer/Explanation
Limestone is used to make calcium oxide, to neutralise acidic industrial waste, and to treat acidic soil.
It is not used to purify water — that process typically uses filtration and chlorination instead.
✅ Answer: (C)
It is not used to purify water — that process typically uses filtration and chlorination instead.
✅ Answer: (C)
▶️ Answer/Explanation
Row A actually shows ethene (C=C double bond), not methane, and row B shows ethanol (with –OH), not ethene, so both are mislabelled.
Row C correctly shows the saturated two-carbon structure \( C_2H_6 \) labelled as ethane, matching its structure and name.
✅ Answer: (C)
Row C correctly shows the saturated two-carbon structure \( C_2H_6 \) labelled as ethane, matching its structure and name.
✅ Answer: (C)
▶️ Answer/Explanation
The speed–time graph shows speed increasing steadily with time, so the object accelerates throughout.
Since distance covered per unit time grows as speed increases, the distance–time graph must curve with an increasing gradient.
✅ Answer: (D)
Since distance covered per unit time grows as speed increases, the distance–time graph must curve with an increasing gradient.
✅ Answer: (D)
▶️ Answer/Explanation
Total mass of the five balls is \( 5 \times 5.0 = 25\text{ g} \), and total volume displaced is \( 40 – 30 = 10\text{ cm}^3 \).
Density is \( \dfrac{25}{10} = 2.5\text{ g/cm}^3 \).
✅ Answer: (D)
Density is \( \dfrac{25}{10} = 2.5\text{ g/cm}^3 \).
✅ Answer: (D)
▶️ Answer/Explanation
The moment of a force is defined as force multiplied by the perpendicular distance from the pivot.
Here, \( \text{moment} = 10 \times 0.25 \).
✅ Answer: (A)
Here, \( \text{moment} = 10 \times 0.25 \).
✅ Answer: (A)
▶️ Answer/Explanation
A battery stores energy in chemical form within its internal reactants.
When connected in a circuit, this chemical energy is converted into electrical energy to drive a current.
✅ Answer: (A)
When connected in a circuit, this chemical energy is converted into electrical energy to drive a current.
✅ Answer: (A)
▶️ Answer/Explanation
Water is held at height behind a dam, giving it gravitational potential energy.
As it falls and turns turbines, this gravitational potential energy is converted into electrical energy.
✅ Answer: (C)
As it falls and turns turbines, this gravitational potential energy is converted into electrical energy.
✅ Answer: (C)
▶️ Answer/Explanation
The hot ball warms the air directly above it, which becomes less dense and rises by convection.
This carries thermal energy upwards to Q rather than sideways to P, so Q reads higher.
✅ Answer: (C)
This carries thermal energy upwards to Q rather than sideways to P, so Q reads higher.
✅ Answer: (C)
▶️ Answer/Explanation
A plane mirror reflects light without converging or diverging it, so the image size always matches the object.
The image also appears the right way up (upright) and the same distance behind the mirror as the object is in front.
✅ Answer: (B)
The image also appears the right way up (upright) and the same distance behind the mirror as the object is in front.
✅ Answer: (B)
▶️ Answer/Explanation
Speed is calculated as \( \text{speed} = \dfrac{\text{distance}}{\text{time}} \).
Substituting the values, \( \dfrac{639}{1.80} = 355\text{ m/s} \).
✅ Answer: (B)
Substituting the values, \( \dfrac{639}{1.80} = 355\text{ m/s} \).
✅ Answer: (B)
▶️ Answer/Explanation
An electromagnet’s magnetic field exists only while current flows through its coil.
Switching the current on and off rapidly switches the magnetism on and off, unlike a permanent magnet which is always magnetic.
✅ Answer: (A)
Switching the current on and off rapidly switches the magnetism on and off, unlike a permanent magnet which is always magnetic.
✅ Answer: (A)
▶️ Answer/Explanation
In series, both lamps share the same current, so changing one component affects both lamps’ brightness.
Only a parallel branch with its own variable resistor lets one lamp’s brightness change independently of the other, which is the arrangement shown in option B.
✅ Answer: (B)
Only a parallel branch with its own variable resistor lets one lamp’s brightness change independently of the other, which is the arrangement shown in option B.
✅ Answer: (B)
▶️ Answer/Explanation
Two resistors R in parallel give a total resistance of \( \dfrac{R}{2} \), which is less than R.
Since the cell’s voltage is unchanged and total resistance has decreased, by \( I = \dfrac{V}{R} \) the current must be greater than I.
✅ Answer: (C)
Since the cell’s voltage is unchanged and total resistance has decreased, by \( I = \dfrac{V}{R} \) the current must be greater than I.
✅ Answer: (C)
▶️ Answer/Explanation
A fuse must have a rating slightly higher than the normal operating current so it doesn’t blow during normal use.
A 10 A fuse would blow at 11 A, while 13 A is the next standard rating that safely allows normal operation and still protects the circuit.
✅ Answer: (C)
A 10 A fuse would blow at 11 A, while 13 A is the next standard rating that safely allows normal operation and still protects the circuit.
✅ Answer: (C)
▶️ Answer/Explanation
Isotopes must have the same number of protons (same element) but different numbers of neutrons.
Option B is the pair where both nuclei have identical proton counts but differing neutron counts.
✅ Answer: (B)
Option B is the pair where both nuclei have identical proton counts but differing neutron counts.
✅ Answer: (B)