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: Radiology
[{'content': 'Estimation of foetal maturity by hiparietal sonic measurement is accurate to within + -: \nSelect and explain. \nA. 3-7 days, B. 7-10 days, C. 10-15 days, D. 14-20 days', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. 3-7 days', 'role': 'assistant'}]