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': 'Dose of DDT for effective control of mosquitoes is - \nSelect and explain. \nA. 1-2 g/m2, B. 5-6 g/m2, C. 2-4 g/m2, D. 2-4 g/m2', 'role': 'user'}, {'content': "Answer: A \nExplanation: DDT: DDT is an indoor residual spray DDT is the insecticide of choice and dosage of 1-2 grams of pure DDT per sq.metre are applied 1-3 times a year to walls and other surfaces where mosquitoes rest. Duration of effectiveness is 6 to 12 months Park's Textbook of Preventive and Social Medicine, 25th Edition, Pg 833", 'role': 'assistant'}]