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': 'Regarding stones in gall bladder the following are true except - \nSelect and explain. \nA. Mixed stones are common in the west, B. In Saints Triad diverticulosis of colon and hiatus hernia coexist, C. Is a risk factor in the development of GB carcinoma, D. 90% of GB stones are radioopaque', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]