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: Unknown
Which of the following art is a fusion inhibitor? 
Select and explain. 
A. Zidovudine, B. Enfuvirtide, C. Nevirapine, D. Ritonavir
B: Enfuvirtide
Answer: B: Enfuvirtide 
Explanation: (Refer: K. D. Tripathi's Essentials of Medical Pharmacology, 7th edition, pg no:774)