This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gallstone Disease, Subject name: Surgery
[{'content': 'Cause of obstructive jaundice is- \nSelect and explain. \nA. Cystic duct stone, B. CBD stone, C. Hepatitis, D. Liver cirrhosis', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., CBD stone", 'role': 'assistant'}]