**Core Concept**
Nevirapine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) used in the treatment of HIV-1 infection. It works by inhibiting the activity of the reverse transcriptase enzyme, which is crucial for the replication of retroviruses like HIV.

**Why the Correct Answer is Right**
Nevirapine binds to the reverse transcriptase enzyme at a site distinct from the substrate binding site, thereby altering the enzyme's conformation and preventing the binding of nucleoside analogs to the enzyme. This results in the inhibition of viral DNA synthesis and ultimately, the replication of HIV. The binding of Nevirapine to the reverse transcriptase enzyme is highly specific and reversible, allowing for the development of resistance mutations in the virus.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as Nevirapine does not work by inhibiting the protease enzyme. Protease inhibitors, like Saquinavir, work by blocking the protease enzyme, which is essential for the maturation of viral particles.
* **Option B:** This option is incorrect as Nevirapine does not work by activating the immune system. Immune modulators, like Interferon-alpha, work by enhancing the body's immune response to viral infections.
* **Option C:** This option is incorrect as Nevirapine does not work by inhibiting the entry of the virus into host cells. Entry inhibitors, like Maraviroc, work by blocking the binding of the virus to the host cell receptor.

**Clinical Pearl / High-Yield Fact**
Nevirapine is associated with a high risk of hepatotoxicity, particularly during the first 6 weeks of treatment. Regular monitoring of liver function tests is essential to prevent severe liver damage.

**Correct Answer:** C. Non-nucleoside reverse transcriptase inhibitor (NNRTI) that binds to the reverse transcriptase enzyme, inhibiting viral DNA synthesis.