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
Incidence of TB in a community measured by 
Select and explain. 
A. Mantoux test +, B. Tuberculin test +, C. Sputum culture, D. Sputum smear +
D: Sputum smear +
Answer: D: Sputum smear + 
Explanation: None