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': 'All of the following dyes are water soluble except: \nSelect and explain. \nA. Metrizamide, B. lohexol, C. Conray 420, D. Myodil', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Myodil', 'role': 'assistant'}]