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': "Which among the following is the earliest to be detected by an antenatal USG? \nSelect and explain. \nA. Anencephaly, B. Down's syndrome, C. Gender, D. Cleft palate", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Anencephaly can be detected as early as 10 weeks of pregnancy and the diagnosis is 100% accurate.', 'role': 'assistant'}]