Correct Answer: D

Rationale: The Golgi apparatus is responsible for the final stages of protein modification and packaging for secretion in animal cells. After proteins are synthesized in the rough endoplasmic reticulum (RER), they are transported to the Golgi apparatus for further processing, sorting, and packaging before being sent to their final destination within or outside the cell. The smooth endoplasmic reticulum (SER) is mainly involved in lipid metabolism and detoxification processes, not protein modification. Ribosomes are the cellular organelles responsible for protein synthesis, not the final stages of protein modification and packaging for secretion, which is the role of the Golgi apparatus.

Correct Answer: D

Rationale: Carotene is the pigment responsible for the yellow color of bananas. It belongs to a group of plant pigments called carotenoids, which are responsible for giving fruits and vegetables their vibrant colors, including the yellow hue of bananas. Potassium, calcium, and phosphorus are essential minerals found in bananas but are not responsible for their yellow color.

Correct Answer: D

Rationale: Calcitonin is a hormone produced by the thyroid gland that primarily functions to lower blood calcium levels. It achieves this by inhibiting bone breakdown and promoting calcium excretion by the kidneys. Therefore, the correct answer is D as it reflects the main role of calcitonin in calcium homeostasis. Choices A, B, and C are incorrect as they do not align with the primary function of calcitonin. Calcitonin does not stimulate metabolism and heat production (Choice A), increase calcium absorption from the intestines (Choice B), or enhance bone growth and development (Choice C).

Correct Answer: B

Rationale: The balanced chemical equation indicates that 2 moles of H2 react with 1 mole of O2 to produce 2 moles of H2O. To determine how many moles of O2 are required to react with 4 moles of H2, you can use the mole ratio from the balanced equation: 2 moles of H2 react with 1 mole of O2. Therefore, to react completely with 4 moles of H2, you would need 2 moles of O2 (4 moles H2 · 2 moles H2 per 1 mole O2). Hence, 2 moles of oxygen are required to react completely with 4 moles of hydrogen. Choices A, C, and D are incorrect because they do not reflect the correct stoichiometry as defined by the balanced chemical equation.

Correct Answer: B

Rationale: A convex lens focuses parallel light rays to a single point by causing them to converge. This lens is thicker in the center than at the edges, which helps in converging the light rays. Convex lenses are commonly used for tasks like magnification and focusing due to their ability to bring distant light rays to a single focal point. Choice A, the concave lens, diverges light rays rather than converging them, making it incorrect. Choice C, the cylindrical lens, is designed to focus light along one axis rather than converging parallel light rays to a single point. Choice D, the plano lens, has no curvatures to bend or focus light rays, so it does not converge parallel light rays.