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
Percentage of renal stones which are radio opaque ? 
Select and explain. 
A. 10%, B. 25%, C. 37%, D. 90%
D: 90%
Answer: D: 90% 
Explanation: Ans. is `d' i.e. 90%