This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Health programmes in India, Subject name: Social & Preventive Medicine
[{'content': 'In 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: Park's textbook of preventive and social medicine 23rd edition. *API is a sophisticated measure of malaria incidence in a community. It is based on intensive active and passive surveillance and cases are confirmed by blood examination.", 'role': 'assistant'}]