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
Following drugs act against HIV–2 Except : 
Select and explain. 
A. Ritonavir, B. Tenofovir, C. Efavirenz, D. Zalcitabine
C: Efavirenz
Answer: C: Efavirenz 
Explanation: None