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': 'A trained bih attendant serves a population of: \nSelect and explain. \nA. 500, B. 1000, C. 2500, D. 5000', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Each trained bih attendant is meant to serve 1000 population. Ref: Textbook of community medicine, S. Lal, 3rd edition pg: 629.', 'role': 'assistant'}]