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: Gynaecology & Obstetrics
[{'content': 'Most appropriate time for chorionic villi sampling in pregnancy is : \nSelect and explain. \nA. 16-18 weeks, B. 16-20 weeks, C. 9-11 weeks, D. 8-10 weeks', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 9-11 weeks', 'role': 'assistant'}]