The spleen's venous drainage flows into which vein?

Correct Answer: B

Rationale: The splenic vein drains into the hepatic portal vein; renal and vena cava are unrelated.

Correct Answer: B

Rationale: The thymus matures T cells; bone marrow produces them, spleen and nodes activate.

Correct Answer: A

Rationale: Tonsils trap throat pathogens; spleen filters blood, thymus matures T cells, nodes filter lymph.

Correct Answer: C

Rationale: Mast cells mediate type I via IgE; T and B cells are adaptive, neutrophils are innate.

Correct Answer: C

Rationale: NK cells monitor for abnormal cells; B and T cells are adaptive, macrophages phagocytose.