## Core Concept
Neuraminidase inhibitors are a class of antiviral drugs used to treat and prevent influenza A and B infections. They work by inhibiting the neuraminidase enzyme on the surface of the influenza virus, which is essential for the release of new viral particles from infected cells.

## Why the Correct Answer is Right
Zanamivir (Option D) is a neuraminidase inhibitor. It specifically blocks the neuraminidase enzyme, preventing the spread of the virus within the respiratory tract. This action reduces the severity and duration of influenza symptoms. Zanamivir is administered via inhalation.

## Why Each Wrong Option is Incorrect
**Option A:** Oseltamivir is also a neuraminidase inhibitor but is given orally, not matching the specificity of the question towards inhalation or a specific drug.
**Option B:** Amantadine is an adamantane derivative that acts as an M2 ion channel inhibitor, not a neuraminidase inhibitor.
**Option C:** Ribavirin is a nucleoside analogue used in the treatment of respiratory syncytial virus (RSV) and some cases of hepatitis C, not a neuraminidase inhibitor.

## Clinical Pearl / High-Yield Fact
A key point to remember is that neuraminidase inhibitors are most effective when started early in the course of influenza infection. They can reduce the duration of symptoms by approximately 1-2 days when initiated within 48 hours of symptom onset.

## Correct Answer Line
**Correct Answer: D. Zanamivir.**