**Core Concept**
Amyloid is a type of proteinaceous deposit found in various tissues, including the brain, heart, and kidneys. These deposits are composed of fibrillar proteins that are insoluble in water and have a distinctive appearance under the microscope. The identification of amyloid deposits is crucial in diagnosing conditions such as Alzheimer's disease, amyloidosis, and Creutzfeldt-Jakob disease.

**Why the Correct Answer is Right**
The specific stain used to identify amyloid deposits is Congo Red. This stain binds to the amyloid fibrils and causes them to exhibit a characteristic green birefringence when viewed under polarized light. This phenomenon is due to the helical structure of the amyloid fibrils, which allows the Congo Red molecules to align in a specific way and produce the green color. The use of Congo Red staining is a key diagnostic tool in identifying amyloid deposits in tissues.

**Why Each Wrong Option is Incorrect**
* **Option A:** Haematoxylin and Eosin (H&E) staining is a general-purpose stain used to identify various tissue structures, but it is not specific for amyloid.
* **Option B:** Alcian blue staining is used to identify mucopolysaccharides and is not specific for amyloid.
* **Option D:** Periodic acid-Schiff (PAS) staining is used to identify glycogen and other carbohydrates, but it is not specific for amyloid.

**Clinical Pearl / High-Yield Fact**
Remember that Congo Red staining is a key diagnostic tool for identifying amyloid deposits, but it requires polarized light to exhibit the characteristic green birefringence.

**Correct Answer: C. Congo Red.**