Spaces between trabeculae, medullary Cord.

Correct Answer: C

Rationale: Medullary sinuses are spaces between trabeculae and medullary cords in lymph nodes.

Correct Answer: D

Rationale: Thymulin enhances various T-cell functions.

Correct Answer: C

Rationale: Hassall's corpuscles increase with age ; they're in medulla , surrounded by reticular cells not lymphocytes , and are acidophilic .

Correct Answer: C

Rationale: Complement activates via classical (antibody-dependent), alternative (spontaneous), and lectin (mannose-binding) pathways ; other options misname pathways.

Correct Answer: B

Rationale: TCRs (T-cell receptors) are on T cells ; B cells have BCRs, not TCRs.