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
Which of the following drug is used as an antismoking drug 
Select and explain. 
A. Trimethoprim, B. Fluvoxate, C. Biperiden, D. Mecamylamine
D: Mecamylamine
Answer: D: Mecamylamine 
Explanation: Mecamylamine is Nicotine receptor antagonist used against smoking.