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: 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: Ans. is 'b' i.e., 1 year", 'role': 'assistant'}]