This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'How many polypepide chains does insulin compose of ? \nSelect and explain. \nA. 4 chains, B. 3 chains, C. 2 chains, D. 5 chains', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Insulin is two-chain polypeptide hormone, with 51 amino acids. Structure: 2 chains - A & B chain. A - chain - 21 amino acids; B - chain - 30 amino acids. Half-life-: About 5 mins', 'role': 'assistant'}]