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': 'Insecticide of choice for sandfly? \nSelect and explain. \nA. DDT, B. Malathione, C. Paris green, D. None', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., DDT Resistance to DDT has not been demonstrated in sandflies A single application of DDT or lindane has been found effective in reducing sandflies. 7 DDT residue may remain effective for a period of 1 to 2 years and lindane only for a period of 3 months.", 'role': 'assistant'}]