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
Retro peritoneal fibrosis is caused by drug 
Select and explain. 
A. Methysergide, B. Melphalan, C. Cyclosporine, D. All
A: Methysergide
Answer: A: Methysergide 
Explanation: ,