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: Medicine
[{'content': 'The genetic variation in drug metabolism pathway that results in severe toxicity of fluorouracil is: \nSelect and explain. \nA. CYP2C9, B. Dihydropyrimidine dehydrogenase, C. Thiopurine-S methyltransferase, D. CYP2D6', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Genetic variation in drug metabolism pathway dihydropyrimidine dehydrogenase results in severe toxicity of capecitabine, fluorouracil. Ref: Harrison, Edition-18, Page-42.', 'role': 'assistant'}]