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: Surgery
[{'content': 'Secondary bladder stone formed due to \nSelect and explain. \nA. BPH, B. Bladder diverticulum, C. Foreign body, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Causes for Secondary bladder stone are BPH\n\nBladder diverticulum\nForeign body.', 'role': 'assistant'}]