Explanation

Key disputed: as transcribed, this question is defective. Oxytocin is a nonapeptide, corticotropin (ACTH) is a 39-amino-acid peptide, and insulin consists of two disulphide-linked peptide chains (51 amino acids) - so options (A), (B) and (C) ALL contain peptide chains, while cortisone (D) is a steroid derived from cholesterol and contains no peptide chain. The official UPSC answer key marks (D), which is coherent only if the original paper asked which hormone does NOT contain a peptide chain (the word 'not' was likely dropped in transcription). Cortisone is the sole non-peptide hormone in the list, hence (D) per the official key.