This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Demography and family planning, Subject name: Social & Preventive Medicine
[{'content': 'National Family Health Survey is done every \nSelect and explain. \nA. 6 months, B. 1 year, C. 5 years, D. 10 years', 'role': 'user'}, {'content': 'Answer: B \nExplanation: National family health survey is conducted during every 1 year Reference: Park&;s textbook of preventive and social medicine, 23rd edition', 'role': 'assistant'}]