This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thyroid Gland, Subject name: Surgery
Which of the following is used in the treatment of well differentiated thyroid carcinoma: 
Select and explain. 
A. I-131, B. Technetium Scan, C. Phosphate, D. MIBG
A: I-131
Answer: A: I-131 
Explanation: Ans. (a) I131Ref: Schwartz 10th edition, Page 1543* I131 is used in the treatment of metastatic well differentiated cancers.* I123, Tc 99m are all used only for diagnostic purposes.