## Core Concept
Selenium sulphide is an antifungal and antibacterial agent used in dermatology for its keratolytic and antiseborrheic properties. It is commonly used to treat conditions caused by yeast and other fungi. The mechanism involves disrupting the cell membrane of fungi, ultimately leading to cell death.

## Why the Correct Answer is Right
The correct answer, **D. Tinea versicolor**, is a skin condition caused by an overgrowth of yeast on the skin, specifically *Malassezia* species. Selenium sulphide helps in reducing the flaking and redness associated with this condition by slowing down the growth of yeast and reducing scaling.

## Why Each Wrong Option is Incorrect
- **Option A:** While selenium sulphide can be used for conditions like dandruff and seborrheic dermatitis due to its antiseborrheic properties, the question seems to focus on a more specific antifungal indication.
- **Option B:** This option seems to be missing but typically, selenium sulphide is not primarily indicated for conditions like acne, which is more commonly treated with antibiotics, retinoids, or hormonal therapies.
- **Option C:** Similarly, this option appears to be incomplete but given the context, conditions like psoriasis might be treated with selenium sulphide for its keratolytic properties, but it's not the best fit compared to its use in tinea versicolor.

## Clinical Pearl / High-Yield Fact
A key point to remember is that selenium sulphide can cause skin and hair discoloration and should be used with caution, especially on colored hair. It's also important to note that tinea versicolor can recur, and maintenance therapy may be necessary.

## Correct Answer: D. Tinea versicolor.