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
Mechanism of action of prophylthiouracil ? 
Select and explain. 
A. Prevents synthesis of thyroglobulin, B. Prevents iodine trapping, C. Prevents release of T4 & T3, D. Inhibits coupling
D: Inhibits coupling
Answer: D: Inhibits coupling 
Explanation: Ans. is 'd' i.e., Inhibits coupling