function of macrophage

Correct Answer: D

Rationale: Macrophages phagocytose debris , destroy erythrocytes , and contribute to iron metabolism (part of B); all apply.

Correct Answer: C

Rationale: C3 is the most abundant complement protein , central to all activation pathways; C1, C2, C4 are less abundant.

Correct Answer: A

Rationale: TCRs are alpha-beta or gamma-delta; AB/CD/YD/CD are not standard notations.

Correct Answer: B

Rationale: Central tolerance ensures T cells recognize self-MHC without attacking self ; not just foreign , not attack self , not B cells .

Correct Answer: A

Rationale: B cells need antigen binding to BCRs and T-helper cytokines ; no twin T cells , RBCs , or antibody-macrophage mechanism activate them.