With regard to the medullary sinuses of the lymph node: They are traversed by reticular cells.

Correct Answer: A

Rationale: Reticular cells form a network across medullary sinuses, aiding in lymph filtration.

Correct Answer: A

Rationale: Primary follicles lack germinal centers and are rich in B-lymphocytes, with few T-lymphocytes.

Correct Answer: C

Rationale: PALS is the thymus-dependent zone in the spleen, rich in T-lymphocytes.

Correct Answer: C

Rationale: Blood-thymic barrier has continuous endothelium and thick basement , protects immature T-cells ; T-lymphocytes are in both cortex and medulla, but immature are in cortex (C is incorrect).

Correct Answer: D

Rationale: Lingual tonsils have ducts opening at crypt bases, reducing inflammation by clearing debris ; location and epithelium don't fully explain (A, B), surface ducts are incorrect .