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
Radio-luscent renal stones are composed of ? 
Select and explain. 
A. Cysteine, B. Calcium phosphate, C. Uric acid, D. All
C: Uric acid
Answer: C: Uric acid 
Explanation: Ans is i.e., 'c' i.e. Uric acid Pure uric acid stones are radiolucent but uric acid stone usually contains calcium and are opaque.