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': 'The best way of diagnosing Trisomy-21 during second trimester of pregnancy is : \nSelect and explain. \nA. Triple marker estimation, B. Nuchal skin fold thickness measurement, C. Chorionic villus sampling, D. Amniocentesis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans is d i.e. Amniocentesis', 'role': 'assistant'}]