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: Pediatrics
[{'content': 'Pseudo hermaphroditism in a female child is most commonly due to: \nSelect and explain. \nA. 21-hydroxylase deficiency, B. 17-hydroxylase deficiency, C. 11-hydroxylase deficiency, D. 3-hydroxylase deficiency', 'role': 'user'}, {'content': "Answer: A \nExplanation: a. 21-hydroxylase deficiency(Ref: Nelson's 20/e p 2714-2723, Ghai 8/e p 526-527)Classic 21-hydroxylase deficiency is the most common cause of ambiguous genitalia in a female newborn. Virilization is usually apparent at birth in females, i.e. Pseudo hermaphroditism of a female child.", 'role': 'assistant'}]