**Core Concept**
Pityriasis versicolor is a superficial fungal infection caused by Malassezia species, leading to patches of discoloration on the skin. Effective treatment involves antifungal agents that target the fungal cell membrane.

**Why the Correct Answer is Right**
The correct answer is a topical antifungal agent that works by inhibiting the enzyme lanosterol 14α-demethylase, which is essential for the conversion of lanosterol to ergosterol in the fungal cell membrane. This disruption of ergosterol synthesis leads to the accumulation of toxic compounds and ultimately causes fungal cell death. The correct agent is also lipophilic, allowing it to penetrate the stratum corneum and reach the affected Malassezia yeast.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a topical corticosteroid, which is not effective against fungal infections and may even exacerbate the condition by promoting fungal growth.
**Option B:** This option is incorrect because it is a topical antibiotic, which has no effect on fungal infections caused by Malassezia species.

**Clinical Pearl / High-Yield Fact**
Remember that Malassezia species thrive in warm, oily areas of the body, such as the scalp, face, and upper trunk. Effective treatment of pityriasis versicolor requires a combination of good hygiene, topical antifungal agents, and avoidance of exacerbating factors such as excessive sweating and tight clothing.

**Correct Answer: C. Ketoconazole**