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
The following drugs are used in obesity, except: 
Select and explain. 
A. Orlistat, B. Sibutramine, C. Olestra, D. Neuropeptide Y Agonist
D: Neuropeptide Y Agonist
Answer: D: Neuropeptide Y Agonist 
Explanation: Neuropeptide Y Antagonist are used in the medical management of obesity; Neuropeptide Y Agonist are not anti-obesity drugs. While Orlistat, Silbutramine and Olestra are used in the treatment of obesity. Ref: K D Tripathi Textbook of Pharmacology, 5th Edition, Pages 117-18; Obesity: Pathophysiology, Psychology and Treatment By George L. Blackburn, Beatrice Stefannie Kanders, Pages 283-99 3. Concise Dictionary of Pharmacological Agents: Propeies and Synonyms By Dr. Ian Moon, Ian K. M. Moon, Judith M. Hall, Dr. Judith Hall, Page 192