This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Biochemistry
[{'content': 'Rate limiting enzyme in testosterone synthesis \nSelect and explain. \nA. 17,20 lyase, B. 20,22-desmolase, C. 3-bHSD, D. 17-hydroxylase', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Cholesterol is first acted upon by desmolase and a 6-carbon unit is cleaved off, forming 21 carbon steroid, pregnenolone It is the common precursor for all the steroid hormonesRef: DM Vasudevan, 7th edition, page no: 664', 'role': 'assistant'}]