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: Pathology
[{'content': 'Most common cause of congenital adrenal hyperplasia: Maharashtra 10 \nSelect and explain. \nA. 21-Hydroxylase deficiency, B. 11-Hydroxylase deficiency, C. 17-a-Hydroxylase deficiency, D. 3-P-Hydroxy dehydrogenase deficiency', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. 21-Hydroxylase deficiency', 'role': 'assistant'}]