## Core Concept
The question tests knowledge of microbiological staining techniques, specifically for identifying fungal elements. Fungal stains are crucial in diagnosing fungal infections, and the choice of stain depends on the type of specimen and the suspected fungus.

## Why the Correct Answer is Right
The correct answer, **Gomori Methenamine Silver (GMS)**, is a widely used stain for detecting fungi in tissue samples. It is particularly useful because it reacts with the polysaccharide walls of fungi, staining them black against a lighter background. This makes it easier to visualize fungal elements, such as hyphae and yeast, in histopathological specimens.

## Why Each Wrong Option is Incorrect
* **Option A: Gram stain** - While the Gram stain can be used to identify some fungi, it is not the best stain for visualizing fungal elements, especially in tissue samples. Gram stain is more commonly used for bacteria.
* **Option B: Ziehl-Neelsen stain** - This stain is primarily used to identify acid-fast bacteria, such as Mycobacterium species, and is not suitable for staining fungi.
* **Option D: Periodic Acid-Schiff (PAS)** - Although PAS can stain fungi, it is not as specific for fungi as GMS. PAS is used to detect polysaccharides in tissue samples and can stain other structures besides fungi.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **GMS and PAS** are both useful stains in the histopathological diagnosis of fungal infections. GMS is particularly favored for its specificity to fungi, making it a valuable tool in diagnosing invasive fungal infections.

## Correct Answer: C. Gomori Methenamine Silver (GMS).