This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gallstone Disease, Subject name: Surgery
[{'content': 'Radio-opaque gall stones - \nSelect and explain. \nA. 10%, B. 20%, C. 30%, D. 40%', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., 10% o Only about 15% gallstones contain enough calcium to render them radioopaque,o Calcium bilirubinate if present in significant amount in gallstones makes them radioopaque,", 'role': 'assistant'}]