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
All the following radioisotopes are used in painful body metastasis except 
Select and explain. 
A. Strontium-89, B. Samarium-153, C. Tin-117, D. Yttrium
D: Yttrium
Answer: D: Yttrium 
Explanation: Yttrium is used in Medical Synovectomy.