This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Pharmacology
[{'content': 'Anti-smoking drug is? \nSelect and explain. \nA. Theophylline, B. Biclutamide, C. Salmeterol, D. Varenicline', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) VareniclineRef Harrison 17/e, chapter 390', 'role': 'assistant'}]