This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thyroid Malignancies, Subject name: Surgery
Which of the following is used in the treatment of well differentiated thyroid carcinoma - 
Select and explain. 
A. Il31, B. 99m Tc, C. 32p, D. MIBG
A: Il31
Answer: A: Il31 
Explanation: Ans. is 'a' i.e., I131