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
Secondary bladder stone formed due to 
Select and explain. 
A. BPH, B. Bladder diverticulum, C. Foreign body, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Causes for Secondary bladder stone are BPH

Bladder diverticulum
Foreign body.