**Core Concept**
The facial muscles responsible for facial expressions are innervated by the facial nerve (cranial nerve VII) and are divided into two main groups: the muscles of facial expression and the muscles of facial mimetic expression. The muscles of facial expression are primarily responsible for controlling the movement of the face, including frowning, smiling, and other emotions.

**Why the Correct Answer is Right**
The muscle responsible for frowning is the corrugator supercilii. This muscle is a thin, fan-shaped muscle located in the forehead that contracts to pull the eyebrows downward and medially, resulting in a frowning expression. The corrugator supercilii muscle is innervated by the facial nerve (cranial nerve VII) and is one of the key muscles involved in facial expressions.

**Why Each Wrong Option is Incorrect**
* **Option A:** The zygomaticus major muscle is responsible for smiling, not frowning. It contracts to pull the corners of the mouth upward and outward, resulting in a smiling expression.
* **Option B:** The procerus muscle is involved in wrinkling the forehead, but it is not the primary muscle responsible for frowning. It works in conjunction with the corrugator supercilii muscle to create a frowning expression.
* **Option C:** The orbicularis oculi muscle surrounds the eye and is responsible for eye movements, including closing the eyelids. It is not involved in frowning.

**Clinical Pearl / High-Yield Fact**
The facial nerve (cranial nerve VII) is responsible for controlling the muscles of facial expression, including the corrugator supercilii muscle. Damage to the facial nerve can result in weakness or paralysis of the facial muscles, leading to difficulty with facial expressions and eye movements.

**Correct Answer:** C.