This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Statistical Tests, Subject name: Social & Preventive Medicine
[{'content': 'Registration of birth should be done: \nSelect and explain. \nA. Within 15 days, B. After 21 days, C. Before 21 days, D. Within 30 days', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. (c) Before 21 daysRef : K. Park 23rd ed. / 840-41Registration of Some Vital Events* Birth: before 21 days* Death: before 21 days* Marriage: before 30 days', 'role': 'assistant'}]