This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urolithiasis, Subject name: Surgery
Which renal stone is radiolucent? 
Select and explain. 
A. Calcium oxalate, B. Calcium phosphate, C. Uric acid, D. Struvite
C: Uric acid
Answer: C: Uric acid 
Explanation: Ans. (c) Uric acidRef: Robbiris 8thed Table 20-12, Sabiston Textbook of Surgery, 18thed chapter 77,