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
HIV prevalence can be assessed by- 
Select and explain. 
A. Sentinel surveillance, B. Active, C. Passive, D. Register
A: Sentinel surveillance
Answer: A: Sentinel surveillance 
Explanation: Ans. is 'a' i.e., Sentinel surveillance o Sentinel surveillance in India is done in national AIDS control programme.