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': 'An example of a isotope that is predominantly a beta emitter is \nSelect and explain. \nA. 125 Iodine, B. 32 Phosphorus, C. 51 Chromium, D. 99m Technetium', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]