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: Pharmacology
Fastest acting Antithyroid medication is: 
Select and explain. 
A. Pottasium iodide, B. Propylthiouracil, C. Carbimazole, D. Methamizole
A: Pottasium iodide
Answer: A: Pottasium iodide 
Explanation: Pottasium iodide