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': 'Radioisotope used systemically in Polycythemia rubra vera. \nSelect and explain. \nA. 32p, B. 131I, C. Strontium-89, D. Rhenium-186', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 32p - Polycythemia rubra vera.\nRhenium -186; Painful bone metastasis.', 'role': 'assistant'}]