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: Radiology
[{'content': 'Ioc in Choledocholithiasis \nSelect and explain. \nA. USG, B. MRCP, C. ERCP, D. HIDA Scan', 'role': 'user'}, {'content': 'Answer: B \nExplanation: IoC for Cholelithiasis - USG\nIoC for Choledocholithiasis - MRCP.', 'role': 'assistant'}]