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': 'Contrast used in CT : \nSelect and explain. \nA. Gadolinium, B. Technitium, C. Iodine, D. Chromium', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Iodine', 'role': 'assistant'}]