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 among the drugs given below, does NOT act by protease inhibition? 
Select and explain. 
A. Ritonavir, B. Saquinavir, C. Nelfinavir, D. Zanamivir
D: Zanamivir
Answer: D: Zanamivir 
Explanation: None