Which of the following cells plays a central role in the development of an immune response?

Correct Answer: D

Rationale: T-helper cells coordinate immunity; macrophages present antigens, neutrophils fight infection, and T-cytotoxic kill cells.

Correct Answer: B

Rationale: The thymus matures T cells; it doesn't filter lymph , produce antibodies , or just store cells .

Correct Answer: A

Rationale: The right lymphatic duct empties into the right subclavian vein ; left subclavian is for thoracic duct, others (C, D) are indirect.

Correct Answer: C

Rationale: It transports fats from the gut; carbs , proteins , and vitamins are mainly blood-transported.

Correct Answer: B

Rationale: Skeletal muscle movement propels lymph; heart and arteries move blood, gravity aids minimally.