This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Physiology
[{'content': 'The rate-limiting step in the synthesis of coisol is catalyzed by \nSelect and explain. \nA. 21-Hydroxylase, B. 3b-Hydroxysteroid dehydrogenase, C. Cholesterol side-chain cleavage enzyme, D. 11b-Hydroxylase', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The first and rate-limiting step in all steroid biosynthesis is catalyzed by cholesterol sidechain cleavage enzyme, resulting in pregnenolone and isocaproic acid.', 'role': 'assistant'}]