During positive selection, a weak interaction between an immature T cell receptor and self MHC:

Correct Answer: A

Rationale: Weak TCR-MHC binding during positive selection ensures T cells can recognize self-MHC, surviving to mature.

Correct Answer: D

Rationale: Type IV is T-cell-mediated (delayed); Types I-III (A, B, C) involve antibodies.

Correct Answer: C

Rationale: Monoclonal antibodies target one epitope ; not broad antigens or cells (B, D).

Correct Answer: B

Rationale: Cell-mediated immunity involves T cells recognizing antigens; not phagocytosis or humoral .

Correct Answer: C

Rationale: Hapten is a small molecule; they can act as antigen if it binds to a larger protein molecule, unlike viruses (complete antigens) or 'Miligen' (not a real term).