## **Core Concept**
The question tests knowledge of antifungal medications used to treat candidiasis, specifically focusing on orally effective drugs. Candidiasis is a fungal infection caused by *Candida* species, and the treatment often involves antifungal agents. Orally effective drugs are crucial for patient compliance and for treating systemic infections.

## **Why the Correct Answer is Right**
Fluconazole (Option C) is an orally effective triazole antifungal agent. It works by inhibiting the synthesis of ergosterol, a critical component of fungal cell membranes, through the inhibition of **lanosterol 14α-demethylase**. This leads to cell membrane disruption and ultimately inhibits fungal growth. Fluconazole is effective against a wide range of *Candida* species and is commonly used for treating mucosal and systemic candidiasis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Griseofulvin is an antifungal but is primarily used for dermatophyte infections (like ringworm) and not effective against *Candida* species. It works by disrupting microtubule function.
- **Option B:** Nystatin is a polyene antifungal effective against *Candida* but is not orally effective for systemic infections due to poor absorption; it's mainly used for topical and gastrointestinal infections.
- **Option D:** Amphotericin B is a polyene antifungal effective against systemic fungal infections, including candidiasis. However, it is not orally effective due to poor absorption and is usually administered intravenously.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that fluconazole is a first-line treatment for many forms of candidiasis, including oropharyngeal and esophageal candidiasis in immunocompromised patients. However, resistance can occur, particularly in *Candida krusei* and some strains of *Candida albicans*.

## **Correct Answer:** C. Fluconazole.