Which of the following reagent is used to distinguish the C-terminal end in a polypeptide?

Hydrazine

The answer to the question is (a) hydrazine.

Hydrazine is a reagent that reacts with the free carboxyl group of the C-terminal amino acid in a polypeptide. This reaction produces a hydrazide, which can be easily detected. However, hydrazine is not as specific as 2, 4-dinitro fluoro benzene, as it can also react with other functional groups in a polypeptide.