Choose the correct statement concerning the lymphatic vessels:

Correct Answer: C

Rationale: Lymphatic vessels have bicuspid valves, giving a beaded appearance ; they have thin walls and variable diameters.

Correct Answer: C

Rationale: Hyperactivation is the highest macrophage activation state, beyond resting or basic activation ; MHC II upregulation is a feature, not a state.

Correct Answer: A

Rationale: NKT cells have limited TCR diversity ; gamma-delta and alpha-beta T cells have broader repertoires.

Correct Answer: B

Rationale: Natural Treg cells suppress self-reactive T cells ; they don't activate , target B cells , or cause hypermutation .

Correct Answer: A

Rationale: Thymus is a primary lymphoid organ; lymph node , sinus , and nodule are secondary lymphoid structures.