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': '80 % of gall stones contain \nSelect and explain. \nA. Bile pigments, B. Cholesterol, C. Calcium salts, D. Phospolipids', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Answer- B. CholesterolTypes of gall stones-1. CholesterolPure cholesterol (10%)Mixed (70%)2. PigmentBlack pigment stonesBrown pigment stones', 'role': 'assistant'}]