This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
[{'content': 'Bih is to be registered within- \nSelect and explain. \nA. 7 days, B. 14 days, C. 21 days, D. 30 days', 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]