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': 'Isotope used in RAIU \nSelect and explain. \nA. I131, B. I123, C. I125, D. I127', 'role': 'user'}, {'content': 'Answer: D \nExplanation: B i.e. I123', 'role': 'assistant'}]