Step 1: Understanding the Concept:
This is a direct definition-matching question from basic immunology. Instead of reasoning term by term, we can pin down two matches instantly from memory and use elimination to get the other two.
Step 2: Key Formula or Approach:
Two facts are almost unmistakable: cyclosporin is the classic calcineurin-blocking immunosuppressant used in transplant medicine, and a hapten by definition only becomes immunogenic once attached to a carrier. Once Q and S are fixed, only two descriptions remain for P and R, and only one assignment keeps both terms correctly matched.
Step 3: Detailed Explanation:
Fix Q-1 first: cyclosporin blocking calcineurin (description 1) is a well known transplant-pharmacology fact.
Fix S-3 next: a hapten needing a carrier to trigger a response (description 3) is the textbook definition of a hapten.
That leaves descriptions 2 and 4 for P (J gene) and R (epitope).
An epitope is, by definition, the region on an antigen that an antibody physically attaches to, so R must be 2 ("antibody binding site on a large molecule").
By elimination, P (J gene) must be 4 ("contributes to antibody diversity"), which also fits since J segments are part of V(D)J recombination that generates antibody variety.
So the full match is P-4, Q-1, R-2, S-3.
Step 4: Final Answer:
This combination corresponds to option (C): P-4; Q-1; R-2; S-3.