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
[{'content': 'Percentage of renal stones which are radio opaque ? \nSelect and explain. \nA. 10%, B. 25%, C. 37%, D. 90%', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is `d' i.e. 90%", 'role': 'assistant'}]