This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'usually gall stones consists of these types expect \nSelect and explain. \nA. Oxalates, B. Bile salts, C. Bile pigments, D. Cholesterol', 'role': 'user'}, {'content': 'Answer: A \nExplanation: There are two general Clsses of hailstones :cholesterol stones containing more than 50 percbt6of crystalline cholesterol monohydrate and pigmrny6stones composed predominantly of bilirubin calcium salts', 'role': 'assistant'}]