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': 'Incidence of TB in a community measured by \nSelect and explain. \nA. Mantoux test +, B. Tuberculin test +, C. Sputum culture, D. Sputum smear +', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]