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': 'What serves as a precursor of testosterone? \nSelect and explain. \nA. Aldosterone, B. Estrone, C. Methyltestosterone, D. Pregnenolone', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Cholestrol is first acted upon by desmolase and 6 carbon unit cleaved off,forming the 21 carbon steriod, pregnenolone It is common precursor for all steriod hormonesRef: DM Vasudevan, 7th edition, page no: 664, 665, 666', 'role': 'assistant'}]