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
The drug used to treat acyclovir resistant Herpes Simplex Virus (HSV) and Varicella Zoster Virus (VZV) infection is : 
Select and explain. 
A. Foscarnet, B. Valacyclovir, C. Abacavir, D. Ganciclovir
A: Foscarnet
Answer: A: Foscarnet 
Explanation: None