Complete the following sentence. A genetic feature that contributes to the diversity of MHC molecules involves....

Correct Answer: A

Rationale: MHC diversity arises from codominant expression of alleles from both parental haplotypes, enhancing antigen presentation variety.

Correct Answer: A

Rationale: Isotypes (e.g., IgG, IgM) differ in heavy chain constant regions ; variable regions (B, D) determine specificity, not isotype.

Correct Answer: D

Rationale: All (A, B, C) can cause autoantibodies; thus, D is correct.

Correct Answer: C

Rationale: IgG is abundant in newborns via maternal transfer; IgM rises later.

Correct Answer: A

Rationale: Innate immunity is present at birth; acquired (B, C) develops later.