**Core Concept**
Impression materials are used in dentistry to create a replica of the patient's mouth and teeth. They can be classified into two main categories: rigid and elastic. Rigid impression materials maintain their shape and do not change significantly when removed from the mouth.

**Why the Correct Answer is Right**
The correct answer is a type of impression material that is known for its rigidity. It is typically used for making accurate impressions of the teeth and surrounding tissues, especially in cases where a high degree of accuracy is required. This material is often used for creating dental casts and study models.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is a type of elastic impression material, which means it is flexible and can change shape when removed from the mouth.
* **Option B:** This option is incorrect because it is a type of impression material that is used for making impressions of the edentulous (toothless) areas of the mouth, and it is not rigid in nature.
* **Option D:** This option is incorrect because it is a type of impression material that is used for making impressions of the soft tissues of the mouth, and it is not rigid in nature.

**Clinical Pearl / High-Yield Fact**
One key thing to remember is that rigid impression materials are often more accurate than elastic materials, but they can be more difficult to remove from the mouth.

**Correct Answer:** C. Zinc Oxide Eugenol