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: Pharmacology
[{'content': 'Sodium 2–mercapto ethane sulfonate is used as a protective agent in: \nSelect and explain. \nA. Radiotherapy, B. Cancer chemotherapy, C. Lithotripsy, D. Hepatic encephalopathy', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Sodium-2-mercapto ethane sulfonic acid (mesna) is used to ameliorate hemorrhagic cystitis caused by cyclophospha\xadmide and ifosfamide.', 'role': 'assistant'}]