**Core Concept**
Actinomycosis is a chronic bacterial infection caused by Actinomyces species, typically Actinomyces israelii. The hallmark of actinomycosis is the formation of "sulphur granules," which are actually colonies of bacteria.

**Why the Correct Answer is Right**
Sulphur granules are formed when Actinomyces species aggregate and form a dense, yellowish cluster of bacteria. This aggregation is a result of the bacteria's ability to produce a tough, fibrous matrix that protects them from the host's immune response. The sulphur granules are often found in the tissues of infected individuals, and they can be seen as a characteristic feature of actinomycosis under microscopic examination.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** Not applicable.
* **Option C:** Not applicable.
* **Option D:** Not applicable.

**Clinical Pearl / High-Yield Fact**
Sulphur granules are typically found in the tissues of individuals with actinomycosis, and they can be seen as a characteristic feature of the disease under microscopic examination. However, it's worth noting that the presence of sulphur granules is not exclusive to actinomycosis, and they can be found in other conditions as well.

**Correct Answer: C. Clusters of Actinomyces species**