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': 'The following is true about bladder stones ? \nSelect and explain. \nA. Girls more than boys, B. Treatment is lithopexy, C. Always forms in kidneys and passes down to bladder, D. Usually asymptomatic', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Treatment is lithopexy", 'role': 'assistant'}]