**Core Concept**
The question is testing the ability to identify a specific histopathological stain used to differentiate Cryptococcus from other fungi. Cryptococcus is a type of encapsulated yeast that can cause cryptococcosis, particularly in immunocompromised patients.

**Why the Correct Answer is Right**
The correct answer is India ink stain, also known as nigrosin stain. This stain is used to highlight the polysaccharide capsule surrounding Cryptococcus neoformans, making it easily distinguishable from other fungal organisms. The capsule is composed of glucuronoxylomannan, which does not stain with India ink, creating a clear halo around the yeast cells.

**Why Each Wrong Option is Incorrect**
**Option A:** Methenamine silver stain is a type of fungal stain that highlights the cell walls of fungi, but it does not specifically differentiate Cryptococcus from other fungi.
**Option B:** PAS (Periodic Acid-Schiff) stain is a general-purpose stain for carbohydrates, including the capsules of some fungi, but it is not specific for Cryptococcus.
**Option C:** Wright's stain is a general-purpose stain for blood smears and tissue sections, but it is not used to differentiate Cryptococcus from other fungi.

**Clinical Pearl / High-Yield Fact**
Remember that the India ink stain is a classic diagnostic tool for Cryptococcus, and its use is particularly important in the diagnosis of cryptococcal meningitis, a common complication of HIV/AIDS.

**Correct Answer: D. India ink stain.**