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
A case of TB a/c to WHO is detected by 
Select and explain. 
A. Elisa, B. Mass Miniature radiography, C. Sputum exam, D. Montoux test
C: Sputum exam
Answer: C: Sputum exam 
Explanation: None