This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'Insecticied of choice for sandfly? \nSelect and explain. \nA. DDT, B. HCH, C. Malathione, D. Paris green', 'role': 'user'}, {'content': "Answer: A \nExplanation: The insecticide used to control sandflies is a single application of 1 to 2 gm/sq.meter of DDT or 0.25g/sq.meter is found to be effective DDT residue may remain effective for a period of 1-2 years and lindane only for 3 months. Park's Textbook of Preventive and Social Medicine, 25th Edition, Pg 845", 'role': 'assistant'}]