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: Anatomy
[{'content': 'Barr body appears in female fetus at- \nSelect and explain. \nA. 3 weeks, B. 10 weeks, C. 15 weeks, D. 20 weeks', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]