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': 'Best way to confirm that no stones are left back in the CBD? \nSelect and explain. \nA. Choledochoscope, B. Palpation, C. Cholangiogram, D. ERCP', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. is \'c\' i.e., Cholangiogram o "An operative cholangiogram at time of cholecystectomy will also demonstrate presence or absance of bile duct stones".o "If a CBD exploration was performed and a T-tube left in place, a T-tube cholangiogram is done before its removal".', 'role': 'assistant'}]