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
[{'content': 'Following drugs act against HIV–2 Except : \nSelect and explain. \nA. Ritonavir, B. Tenofovir, C. Efavirenz, D. Zalcitabine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]