Correct Answer: D

Rationale: Magnesium plays a key role in muscle relaxation, enzyme operation, and protein synthesis, but it is not directly involved in regulating body temperature.

Correct Answer: B

Rationale: The transport of oxygen in the blood is carried out by hemoglobin, which does not require calcium; instead, calcium is essential for blood clotting, muscle contraction, and nerve transmission.

Correct Answer: A

Rationale: LDL (Low-Density Lipoprotein) is known as the 'bad' type of cholesterol because it deposits cholesterol on the walls of arteries, leading to plaque formation and narrowing of the arteries (atherosclerosis). This narrowing can restrict blood flow and increase the risk of serious cardiovascular conditions. The statement and the reason are directly related because the adherence of LDL to arterial walls and the subsequent narrowing of the lumen are the primary reasons why it is considered detrimental to heart health. Choice B is incorrect because the statement and reason are related. Choice C is incorrect because both the statement and the reason are correct. Choice D is incorrect because the statement correctly identifies LDL as the 'bad' type of cholesterol due to its actions in the arteries.

Correct Answer: C

Rationale: Zinc plays a critical role in wound healing due to its involvement in cell proliferation, immune function, and protein synthesis, all of which are essential for tissue repair.

Correct Answer: D

Rationale: Secretin stimulates the pancreas to release bicarbonate ions to neutralize stomach acid and digestive enzymes into the small intestine.