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: Physiology
[{'content': 'Cause of methaemoglobinemia are all except : \nSelect and explain. \nA. Nitrites, B. Phenacetin, C. Sulfonamide, D. Phenytoin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. Phenytoin', 'role': 'assistant'}]