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': 'Which one of the following is a stomach poison for the larvae of insects of medical importance? \nSelect and explain. \nA. DDT, B. Paris green, C. Pyrethrum, D. Antilarva oil', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Insecticides are substances used to kill insects.\nThey are contact poisons,stomach poisons,fumigants. \nStomach poisons are those which when ingested cause death of the insects. \nExamples are paris green and sodium flouride. DDT and pyrethrum are synthetic and natural contact poisons respectively. \nParks textbook of preventive and social medicine.K Park.', 'role': 'assistant'}]