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': 'Late onset hemorrhagic cystitis after bone marrow transplanatation is caused by: \nSelect and explain. \nA. Cyclophosphamide, B. Ifosfamide, C. Adeno virus, D. Cytomegalo virus', 'role': 'user'}, {'content': 'Answer: C \nExplanation: After bone marrow transplantation (BMT), early-onset hemorrhagic cystitis is related to drugs in the treatment regimen (e.g., cyclophosphamide, ifosfamide), and late-onset hemorrhagic cystitis is usually due to the polyoma virus BKV or adenovirus type 11. Ref: Harrisons principles of internal medicine, 18th edition, Page: 2275.', 'role': 'assistant'}]