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': 'The following are DDT resistant except - \nSelect and explain. \nA. Phlebotomus, B. Culex fatigans, C. Anopheles stephenci, D. Musca domestica', 'role': 'user'}, {'content': "Answer: A \nExplanation: Resistance to DDT has not been demonstrated in Phlebotomus. Organochloride resistance is divided into Resistance to DDT and analogues Resistance to HCH-Dieldrin group of insecticides Park's Textbook of Preventive and Social Medicine, 25th Edition, Pg 845", 'role': 'assistant'}]