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
Radioisotope used systemically in Polycythemia rubra vera. 
Select and explain. 
A. 32p, B. 131I, C. Strontium-89, D. Rhenium-186
A: 32p
Answer: A: 32p 
Explanation: 32p - Polycythemia rubra vera.
Rhenium -186; Painful bone metastasis.