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
Antiviral drug having dual antiviral activity against HIV and HBV is : 
Select and explain. 
A. Enfuvirtide, B. Emtricitabine, C. Abacavir, D. Entecavir
B: Emtricitabine
Answer: B: Emtricitabine 
Explanation: None