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
All of the following are anti HIV agents except ? 
Select and explain. 
A. Ritonavir, B. Acyclovir, C. Didanosine, D. Zidovudine
B: Acyclovir
Answer: B: Acyclovir 
Explanation: Ans. is 'b' i.e., Acyclovir