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
Case finding in RNTCP is based on – 
Select and explain. 
A. Sputum culture, B. Sputum microscopy, C. X-ray chest, D. PCR antibody detection
B: Sputum microscopy
Answer: B: Sputum microscopy 
Explanation: "Sputum microscopy not only confirms the diagnosis, but also indicates the degree of infectivity and response to treatment" - Park
Remember

At least 10000 (104) bacilli should be present per ml of sputum for demonstration in direct smear on ZN staining
Culture can detect 10-100 bacilli per ml of sputum