This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Retro peritoneal fibrosis is caused by drug \nSelect and explain. \nA. Methysergide, B. Melphalan, C. Cyclosporine, D. All', 'role': 'user'}, {'content': 'Answer: A \nExplanation: ,', 'role': 'assistant'}]