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
[{'content': 'Fastest acting antithyroid drug is? \nSelect and explain. \nA. Potassium iodide, B. Propylthiouracil, C. Carbimazole, D. Cholestyramine', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Potassium iodide o Iodine is the fastest acting thyroid inhibitor.", 'role': 'assistant'}]