**Core Concept**
Onychomycosis refers to a fungal infection of the nails, which can be challenging to treat due to the slow growth rate of nails and the possibility of fungal resistance to antifungal agents. Effective management of onychomycosis requires the use of antifungal agents that can penetrate the nail and surrounding tissues, while minimizing side effects.

**Why the Correct Answer is Right**
The most effective and better-tolerated agents in the management of onychomycosis are terbinafine and itraconazole. Terbinafine is a synthetic antifungal agent that inhibits the enzyme squalene epoxidase, which is essential for fungal cell membrane synthesis. This leads to the accumulation of squalene and the disruption of cell membrane integrity, ultimately resulting in fungal cell death. Itraconazole is a triazole antifungal agent that inhibits the enzyme lanosterol 14α-demethylase, which is involved in the conversion of lanosterol to ergosterol, an essential component of fungal cell membranes.

**Why Each Wrong Option is Incorrect**
**Option A:** Griseofulvin is an older antifungal agent that works by inhibiting microtubule formation in fungal cells, but it is less effective and more toxic than terbinafine and itraconazole.
**Option B:** Fluconazole is a triazole antifungal agent that is effective against a wide range of fungal infections, but it is less effective against onychomycosis than terbinafine and itraconazole.
**Option C:** Undecylenic acid is a topical antifungal agent that is often used to treat superficial fungal infections, but it is not effective against onychomycosis.

**Clinical Pearl / High-Yield Fact**
When treating onychomycosis, it's essential to choose an antifungal agent that can penetrate the nail and surrounding tissues effectively. Terbinafine and itraconazole are the most effective options, but they may have different side effect profiles and require different dosing regimens.

**Correct Answer:** C. Undecylenic acid