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 radioisotopes are used as systemic radionucleide, except: \nSelect and explain. \nA. Phosphorus -- 32, B. Strontium -- 89, C. Iridium -- 192, D. Samarium -- 153', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Iridium -- 192', 'role': 'assistant'}]