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: Pathology
[{'content': 'Which of the following is not a Major high risk factor for cholangiocarcinoma: \nSelect and explain. \nA. Chronic typhoid, B. Choledocholithiasis, C. C. sinensis infestation, D. Ulcerative colitis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Choledocholithiasis', 'role': 'assistant'}]