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
Barr body appears in female fetus at- 
Select and explain. 
A. 3 weeks, B. 10 weeks, C. 15 weeks, D. 20 weeks
A: 3 weeks
Answer: A: 3 weeks 
Explanation: None