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: Radiology
Radio opaque stone is 
Select and explain. 
A. Uric acid stone, B. Triamterene, C. Struvite, D. All of the above
C: Struvite
Answer: C: Struvite 
Explanation: Radio opaque stones - Cystine, struvite, calcium oxalate, calcium phosphate.