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
Jack stone calculi are made up of 
Select and explain. 
A. Ammonium urate, B. Uric acid, C. Struvite, D. Calcium oxalate
D: Calcium oxalate
Answer: D: Calcium oxalate 
Explanation: Jack stone calculi are seen in bladder formed by calcium oxalate.