This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infection, Subject name: Medicine
Drug of choice against influenza is - 
Select and explain. 
A. Acyclovir, B. Gancyclovir, C. Zanamivir, D. Indinavir
C: Zanamivir
Answer: C: Zanamivir 
Explanation: Specific antiviral therapy is available for influenza ( Table 187-3 ): the neuraminidase inhibitors zanamivir, oseltamivir, and peramivir for both influenza A and influenza B and the adamantane agents amantadine and rimantadine for influenza A. A 5-day course of oseltamivir or zanamivir reduces the duration of signs and symptoms of uncomplicated influenza by 1-1.5 days if treatment is staed within 2 days of the onset of illness. (Harrison's Principles of internal medicine, 20th edition, page 1497)