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: Surgery
[{'content': 'A retained stone impacted in distal common bile duct is seen on T- tube cholangiogram. What is the best management of stone - \nSelect and explain. \nA. Dissolution therapy, B. Operative removal, C. Endoscopic sphincterotomy and stone extraction, D. No active treatment is required', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]