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
[{'content': 'In an area having annual parasite index of less than 2, the following is to be done – \nSelect and explain. \nA. Passive surveillance only, B. 2 rounds of DDT yearly, C. Entomological surveillance, D. All positive cases blood smear to be done monthly', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]