## Core Concept
The lateral rectus muscle is one of the extraocular muscles responsible for controlling eye movements. It is specifically involved in the abduction of the eyeball. The extraocular muscles are innervated by cranial nerves, which are responsible for transmitting signals from the brain to these muscles.

## Why the Correct Answer is Right
The lateral rectus muscle is supplied by the **abducens nerve**, which is the **6th cranial nerve (CN VI)**. This nerve originates from the pons in the brainstem and exits the skull through the superior orbital fissure to innervate the lateral rectus muscle. The abducens nerve's primary function is to control the lateral rectus muscle, which is responsible for outward gaze or abduction of the eye.

## Why Each Wrong Option is Incorrect
* **Option A:** The **oculomotor nerve (CN III)** supplies several extraocular muscles, including the medial rectus, superior rectus, inferior rectus, and inferior oblique, but not the lateral rectus.
* **Option B:** The **trochlear nerve (CN IV)** innervates the superior oblique muscle, which is involved in the rotation and depression of the eyeball, not the lateral rectus.
* **Option D:** The **ophthalmic nerve (V1)**, a branch of the trigeminal nerve (CN V), is primarily sensory and does not supply any of the extraocular muscles.

## Clinical Pearl / High-Yield Fact
A useful clinical correlation to remember is that the **6th cranial nerve (abducens nerve) is often affected in conditions that increase intracranial pressure**, such as tumors or aneurysms, leading to lateral rectus palsy. This results in diplopia (double vision) that is worse when looking laterally.

## Correct Answer: C. Abducens nerve.