**Core Concept**
The question is about histopathological staining techniques used to visualize specific cellular structures or components. The correct answer will reveal a stain used to highlight a particular feature, such as glycogen, proteins, or cellular inclusions.

**Why the Correct Answer is Right**
The correct stain is used to identify glycogen within cells, which is essential in diagnosing glycogen storage diseases. Glycogen is a complex carbohydrate stored in the liver and muscles. The stain reacts with glycogen to produce a purple color, making it visible under a microscope. This stain is particularly useful in histopathology for identifying glycogen accumulation in various conditions, such as von Gierke's disease and McArdle's disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This stain is not specifically used to identify glycogen.
**Option B:** This stain is used to identify proteins, not glycogen.
**Option C:** This stain is used to identify cellular inclusions, but not specifically glycogen.

**Clinical Pearl / High-Yield Fact**
In histopathology, glycogen storage diseases can be diagnosed by identifying glycogen accumulation in cells using specific stains. This is crucial in differentiating between various types of glycogen storage diseases, which have distinct clinical presentations and management strategies.

**Correct Answer:** C. Periodic Acid-Schiff (PAS)