Explanation:
Choice C is correct because ribosomes are organelles found on the surface of the rough endoplasmic reticulum and are needed to synthesise polypeptide chains.

The nucleus (Choice A) contains DNA, some of which codes for the polypeptides made by the ribosomes. The role of vesicles (Choice B) is to store substances and to transport substances, including proteins, between cellular compartments. The mitochondria (Choice D) are the organelles responsible for aerobic respiration.

Explanation​:
Sieve plates (Statement I) and plasmodesmata (Statement II) are features found in phloem. Sieve plates possess pores which allow continual flow of sap through the sieve tubes. Plasmodesmata are small channels which connect the sieve tube elements to the adjacent companion cells. A high lignin content (Statement III) is found in xylem vessels. It provides support to withstand hydrostatic pressure, and is also impermeable to water.

Explanation​:
The process of air entering the lungs is known as inhalation. The term $\text{“}$inspiration$\text{”}$ is used instead of inhalation sometimes. In order for inhalation to take place, the pressure inside the lungs must be lower compared to atmospheric pressure. To decrease the pressure inside the lungs, the external intercostal muscles must contract and become shorter to pull the ribs up and out, increasing the volume inside the thorax.

Choice A is incorrect because abdominal wall muscles relax during inhalation. Lengthening of the abdominal muscles can contribute to inhalation by pushing the abdominal wall out which increases the volume inside the thorax.

Choice B is incorrect because when the diaphragm relaxes it forms a dome shape and therefore reduces the volume of the thorax. This occurs during exhalation.

Choice D is incorrect because internal intercostal muscles relax and lengthen during inhalation. They contract and shorten during exhalation.

Explanation​:
Choice D is correct because multipotent stem cells can produce only cells of a particular tissue or organ. Choice A is incorrect because pluripotent stem cells are usually found in early embryos and are capable of differentiating to become any cell type found in the organism except for extra-embryonic tissues such as the placenta. Additionally, they are not found in bone marrow. Choice B is incorrect because totipotent stem cells are only found in early stages of embryonic development and can produce all cell types of the organism as well as extra-embryonic tissues such as the placenta. Choice C is incorrect because stem cells are by definition, undifferentiated.

Explanation​:
During exhalation, the diaphragm relaxes and lifts upwards to form a dome shape (Statement I). The internal intercostal muscles contract and pull the ribcage inwards and downwards (Statement II).

This causes the volume inside the thorax to decrease which increases pressure inside the thorax (Statement III). Thus the air is forced out of the lungs.

Explanation​:
Choice A - There are still stem cells that can be found in the adult body. For example, stem cells are present in the bone marrow, skin, and liver.

Choice B - The foetal stage of development happens from the ninth week after conception until birth. In this stage, the organs have begun to form, and these developing organs come from differentiated stem cells.

Choice C - Stem cells are characterised by their capacity to divide and differentiate. These cells are similar to a blank canvas with the possibility of becoming any type of cell.

Choice D - Stem cells are yet to undergo specialisation through the process of differentiation.

Explanation:
The triglyceride molecule consists of one glycerol molecule and three fatty acids.

A phosphate head and two fatty acid tails (Choice A) form a phospholipid, not a triglyceride. One fatty acid and three glycerol molecules (Choice B) or one glycerol molecule and three monosaccharides (Choice D) cannot form a triglyceride.

Explanation:
The disaccharide sucrose is made up of the monosaccharides glucose and fructose. Sucrose forms when glucose and fructose combine in a condensation reaction (a reaction that releases water).

Maltose (Choice A) is a disaccharide made up of two glucose molecules. Lactose (Choice B) is a disaccharide made up of glucose and galactose. Galactose (Choice D) is a monosaccharide, not a disaccharide.

Explanation​:
When two monosaccharides are joined together to form a disaccharide, water is produced, therefore it is a condensation reaction. Choice A is correct.

Choice B is incorrect as hydrolysis uses water to break bonds, in this case converting a disaccharide into a monosaccharides. Choice C is incorrect as catabolism breaks down large molecules into smaller molecules. Choice D is incorrect as oxidation means adding oxygen or losing electrons.

Explanation​:
A potometer is used to measure the rate of transpiration in a plant. When transpiration takes place, water loss occurs because water evaporates inside the leaves and then diffuses out of the leaves. The bubble in the capillary tube will move in the direction of the plant along with the water in the capillary tube which is being absorbed by the plant (Choice C).

Choice B is incorrect because the water and bubble are moving towards the plant, not away from it.

Choice A is incorrect because the water in the reservoir will stay at the same level. The reservoir contains a switch that is used to refill the capillary tube and push the bubble back to the start position. This is done at the end of the experiment to reset the apparatus for the next measurement.

Choice D is incorrect as the water level in the beaker will decrease as water enters the capillary tube and also because of evaporation from the beaker to the atmosphere.

Explanation:
Structure X is a peripheral protein that is attached to one surface of the cell membrane.

Protein channels span the width of membranes (Choice B) as do transmembrane proteins (Choice A). Cholesterol molecules do not have a globular structure (Choice D).

Explanation:
Choice A is correct because a lysosome usually fuses with phagocytic vacuoles containing pathogens or cellular debris, or other vacuoles in the cytoplasm. The enzymes are then released from the lysosome into the vacuole to digest the contents.

Choice B is incorrect because lysosomes contain digestive enzymes that break down cellular components, which involve catabolic reactions, not anabolic reactions. Choice C is incorrect because lysosomes form from vesicles budding off of the Golgi apparatus. Choice D is incorrect because lysosomes are membrane-bound organelles.

Explanation​:
An ecosystem refers to an area where organisms interact with each other and with the physical environment.

A habitat (Choice A) refers to the environment in which a species normally lives. A population (Choice C) is a group of organisms of the same species living in the same area at the same time which can interbreed. A community (Choice D) is a group of populations living and interacting with each other in the same habitat.

Explanation:
Holozoic nutrition refers to the type of nutrition where organisms ingest whole or partially whole food items (Statement II). The ingested food is then broken down by the organism's internal digestive system (Statement III). Therefore Choice B is correct. Saprotrophs (Statement I) are organisms that obtain their nutrients by decomposing dead and decaying organic matter externally and then absorbing the nutrients. Therefore Choices A, C and D are not correct as they all include Statement I.

Explanation​:
Obligate anaerobes are single-celled organisms that will not survive if oxygen is present. Facultative anaerobes are organisms that can either respire aerobically or anaerobically. Obligate aerobes can only respire if oxygen is present and cannot survive in conditions low in oxygen. Therefore Choice A is correct.

Choices B and D are incorrect because obligate anaerobes cannot respire when oxygen is present. Choice C is incorrect as obligate anaerobes require anoxic conditions, and obligate aerobes cannot carry out anaerobic respiration.

Explanation​:
Water is cohesive because it is a polar molecule. The oxygen atom in one water molecule forms a hydrogen bond with the hydrogen atom of another water molecule. In xylem vessels water is attracted to the hydrophilic regions of the cell wall and hydrogen bonds are formed. This an accurate description of the adhesive properties of water in the context of water transport in plants (Choice A). These statements are reversed in Choice D.

Ions dissolve in water, but this is not related to the cohesive (Choice B) or adhesive (Choice C) properties of water.

Explanation:
Protein pumps are membrane proteins that pump molecules up their concentration gradient using energy in the form of ATP.

Protein channels (Choice A) carry out passive transport while receptors (Choice D) and peripheral proteins (Choice C) do not transport proteins.

Explanation:
Regular exercise prevents the buildup of fatty plaque in the coronary arteries thereby preventing heart disease (Choice D). Some of the factors that cause the buildup of fatty plaque and occlusion of the arteries causing chest pain are high blood pressure (Choice A), high blood sugar due to diabetes (Choice B) and some genetic factors (Choice C).

Explanation​:
The enzyme lactase breaks down the substrate lactose into glucose and galactose.

Glucose and galactose are products of the reaction (Choices A and B).

Fructose is not a substrate for the enzyme lactase (Choice D).

Explanation​:
Choice B is correct because incisors are used for biting chunks of food. Choice A is incorrect because tearing is the role of canines. Choices C and D are incorrect because crushing or slicing is the role of the premolars, and grinding is the role of molars.

Explanation​:
Choice D is correct because line transects can be used to show animal or plant distributions. Choices A, B and C are all factors that could be measured using different sensors that could provide meaning to plant or animal distributions.

Explanation:
Centrifugation is a technique that primarily separates substances based on their density. When a mixture is centrifuged, particles or components with higher density sediment to the bottom of the tube. Choice A is, therefore, correct.

Centrifugation does not separate substances based on their charge. Electrophoresis is a technique that separates particles or molecules based on their charge. Choice B is, therefore, incorrect. Centrifugation does not directly separate substances based on their chemical composition. Other techniques like chromatography may be more suitable for separating substances by chemical composition. Choice C is, therefore, incorrect. Centrifugation does not separate substances based on their colour. Colour differences might be observed during centrifugation, but they are not the basis for separation. Choice D is, therefore, incorrect.

Explanation​:
In prokaryotes, the mRNA produced after transcription is ready for translation and does not undergo splicing. In contrast, eukaryotic pre-mRNA undergoes splicing to remove introns and join exons, producing mature mRNA. Choice C is, therefore, correct.

Both prokaryotes and eukaryotes use DNA as a template for transcription. Choice A is, therefore, incorrect. In prokaryotes, transcription occurs in the cytoplasm, while in eukaryotes, it occurs in the nucleus. Choice B is, therefore, incorrect. Splicing of mRNA occurs in eukaryotes, not prokaryotes. Choice D is, therefore, incorrect

Explanation​:
Choice B is correct because Rubisco is the name of the enzyme which is responsible for the fixation of carbon during photosynthesis. Choice A is incorrect as rhodopsin is a pigment found in the retina which is responsible for detecting light . Choices C and D are incorrect as neither are enzymes, with collagen being a structural component of tissues such as skin and insulin being a hormone responsible for regulating blood glucose levels.

Explanation​:
Choice D is correct because starch is made of chains of alpha glucose, proteins are made of chains of amino acids and triglycerides are made of fatty acids and glycerol. Choice A is incorrect because starch is not composed of beta glucose and peptides are not the simplest units of proteins. Choice B is incorrect because starch is not composed of beta glucose and triglycerides do not contain glycogen. Choice C is incorrect because peptides are not the smallest unit of proteins and triglycerides do not contain glycogen.