**Core Concept**
Candidal hyphae are a type of fungal element that can be challenging to identify under routine staining techniques. Specific stains are required to visualize these structures, which are essential for diagnosing candidiasis, a common fungal infection.

**Why the Correct Answer is Right**
Candidal hyphae can be stained using the Periodic Acid-Schiff (PAS) stain, a widely used histochemical technique. PAS stain works by oxidizing the periodic acid, which then reacts with the carbohydrate moieties present in the fungal cell walls, including those of candidal hyphae. This reaction results in a characteristic magenta-colored stain, allowing for the visualization of fungal elements. The use of PAS stain is crucial in the diagnosis of fungal infections, including candidiasis, particularly in tissue sections and biopsies.

**Why Each Wrong Option is Incorrect**
**Option A:** Wright's stain is typically used for staining blood films and is not suitable for staining fungal elements.
**Option B:** Gram stain is used for differentiating between Gram-positive and Gram-negative bacteria and is not effective for staining fungi.
**Option C:** Mucin stain is used for highlighting mucin-containing tissues, such as those found in the gastrointestinal tract, and is not specific for staining fungal elements.

**Clinical Pearl / High-Yield Fact**
Remember that PAS stain is a sensitive and specific stain for detecting fungal elements, including candidal hyphae, in tissue sections and biopsies. This stain is particularly useful in the diagnosis of fungal infections, especially in immunocompromised patients.

**Correct Answer: C. PAS stain.**