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
In an area having annual parasite index of less than 2, the following is to be done – 
Select and explain. 
A. Passive surveillance only, B. 2 rounds of DDT yearly, C. Entomological surveillance, D. All positive cases blood smear to be done monthly
D: All positive cases blood smear to be done monthly
Answer: D: All positive cases blood smear to be done monthly 
Explanation: None