**Core Concept**
The procerus muscle is a facial muscle involved in the movement of the forehead and nose. It plays a role in **facial expression**, particularly in frowning or squinting. The muscle is located in the **glabellar** region.

**Why the Correct Answer is Right**
The procerus muscle is considered a continuation of the **frontalis muscle**, as both muscles work together to control forehead movements. The frontalis muscle is responsible for elevating the eyebrows, while the procerus muscle helps to pull the medial aspect of the eyebrows downward.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as the procerus is not a direct continuation of this muscle.
**Option B:** Similarly, this option does not accurately describe the anatomical relationship of the procerus muscle.
**Option D:** This option is also incorrect as it does not represent the muscle that the procerus is a continuation of.

**Clinical Pearl / High-Yield Fact**
The procerus muscle is clinically relevant in **botulinum toxin injections** for cosmetic purposes, as it can help reduce frown lines.

**Correct Answer:** C. frontalis muscle