Correct Answer: D

Rationale: Macrophages are a type of white blood cell that plays a crucial role in the immune system by engulfing and digesting cellular debris, foreign substances, microbes, cancer cells, and old or damaged cells. Basophils are primarily involved in allergic reactions and parasitic infections, eosinophils combat multicellular parasites and have a role in allergic reactions, and B-cells are responsible for producing antibodies. Therefore, the correct answer is macrophages as they are specialized in phagocytosis and removal of unwanted cells and microorganisms.

Correct Answer: D

Rationale: The correct answer is D: Antidiuretic hormone. Antidiuretic hormone (ADH), also known as vasopressin, is produced by the hypothalamus and stored in the posterior pituitary gland. It plays a key role in regulating the body's water balance by controlling the amount of water reabsorbed by the kidneys. Choices A, B, and C are incorrect because Growth hormone is produced by the anterior pituitary gland, Luteinizing hormone is produced by the anterior pituitary gland, and Adrenocorticotropic hormone is produced by the anterior pituitary gland.

Correct Answer: D

Rationale: Macrophages are a type of white blood cell that plays a crucial role in the immune system by engulfing and digesting cellular debris, foreign substances, microbes, cancer cells, and old or damaged cells. Basophils are primarily involved in allergic reactions and parasitic infections, eosinophils combat multicellular parasites and have a role in allergic reactions, and B-cells are responsible for producing antibodies. Therefore, the correct answer is macrophages as they are specialized in phagocytosis and removal of unwanted cells and microorganisms.

Correct Answer: A

Rationale: The correct answer is the Distal convoluted tubule (DCT). The DCT is the part of the nephron closest to the collecting duct, where the final adjustments to electrolyte and fluid balance are made. Bowman's Capsule is located at the beginning of the nephron, where filtration of blood occurs. The Afferent Arteriole brings blood to the glomerulus for filtration. The Proximal Convoluted Tubule (PCT) is situated after the Bowman's Capsule and is not the part closest to the collecting duct.

Correct Answer: D

Rationale: The correct answer is the aortic valve. The aortic valve is located between the left ventricle and the aorta, preventing the backflow of blood into the left ventricle once it has been pumped out during systole. Choice A, pulmonic, is incorrect as it is associated with the right side of the heart. Choice B, mitral, is incorrect as it is the valve between the left atrium and ventricle. Choice C, tricuspid, is incorrect as it is located between the right atrium and ventricle.