Which of the following is a large genomic region or gene family found in most vertebrates, playing an important role in immunity?

Correct Answer: B

Rationale: MHCs are a large gene family in vertebrates critical for presenting antigens to T cells, distinguishing them from HLAs (a subset of MHC in humans) and other options.

Correct Answer: B

Rationale: NK cells lyse virally infected cells and tumor cells as part of innate immunity, without antigen presentation.

Correct Answer: C

Rationale: The effector phase includes antibody secretion by plasma cells, which have extensive ER for protein production.

Correct Answer: A

Rationale: BCRs undergo somatic hypermutation in B cells to enhance antigen affinity, unlike TCRs or MHCs.

Correct Answer: D

Rationale: Effective immunogens (e.g., proteins) don't require carriers; this is true for haptens, not standalone immunogens.