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': 'Dye used in IV cholangiography is: \nSelect and explain. \nA. Dianosil, B. Conray, C. Billigraffin, D. Myodil', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Billigraffin', 'role': 'assistant'}]