This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anatomy
[{'content': 'Which investigation is being performed? \nSelect and explain. \nA. ERCP, B. MRCP, C. T-tube cholangiography, D. Percutaneous transhepatic Cholangiography', 'role': 'user'}, {'content': 'Answer: C \nExplanation: T-tube seen in the film and a retained CBD stone in the form of a filling defect can be seen in the image.', 'role': 'assistant'}]