This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
Trisodium phosphonoformate (foscarnet) is a potent antiviral agent for treating herpes simplex infections. It works by affecting 
Select and explain. 
A. The viral RNA polymerase, B. The viral DNA polymerase, C. The viral reverse transcriptase, D. The host-cellular DNA polymerase
B: The viral DNA polymerase
Answer: B: The viral DNA polymerase 
Explanation: Trisodium phosphonoformate (foscarnet) inhibits herpes simplex virus (HSV) replication. Foscarnet is a potent inhibitor of HSV-induced DNA polymerase, and has little effect on known cellular DNA polymerases. Herpesvirus mutants resistant to the drug arise easily. To a lesser extent, foscarnet also appears to inhibit the polymerase of hepatitis B virus and retroviruses. Combinations of antivirals, including foscarnet, are currently prescribed to increase the clinical usefulness of the drugs..