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': 'Not a pyrethram derivative? \nSelect and explain. \nA. Cypermethrin, B. Permithrin, C. DDT, D. Resmethrin', 'role': 'user'}, {'content': "Answer: C \nExplanation: park's textbook of preventive and social medicine 23rd edition *synthetic pyrethroids devoloped so far are tetramethrin,resethrin,prothrin and propahin *they are now being devoloped to replace natural pyrethrins some are found to be as much as 10ttimes as effective as naturally occuring pyrethrins .", 'role': 'assistant'}]