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': 'Population coverage of primary health center \nSelect and explain. \nA. 20,000 in plain area, B. 10,000 in tribal area, C. 30,000 in tribal area, D. 30,000 in plain area', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]