**Core Concept**
The ability to look downward is primarily controlled by the muscles that elevate the eye, specifically the superior rectus and inferior oblique muscles. However, the primary muscle responsible for downward gaze is the inferior oblique muscle, which is innervated by the oculomotor nerve (cranial nerve III).

**Why the Correct Answer is Right**
The inferior oblique muscle is responsible for elevating the eye when it is adducted (moved towards the midline) and rotating it outward. It also helps in adduction of the eye. However, a more specific muscle responsible for downward gaze is the superior oblique muscle. The superior oblique muscle is innervated by the trochlear nerve (cranial nerve IV) and is responsible for downward gaze and inward rotation of the eye when it is adducted.

**Why Each Wrong Option is Incorrect**
**Option A:** The superior rectus muscle is primarily responsible for elevation of the eye and is innervated by the oculomotor nerve (cranial nerve III). It is not responsible for downward gaze.

**Option B:** The inferior rectus muscle is primarily responsible for downward gaze but is innervated by the oculomotor nerve (cranial nerve III).

**Option D:** The lateral rectus muscle is primarily responsible for abduction of the eye and is innervated by the abducens nerve (cranial nerve VI).

**Clinical Pearl / High-Yield Fact**
A classic way to remember the muscles of the eye is by the mnemonic "SOAR" for superior oblique, superior rectus, inferior oblique, and inferior rectus. This can help students recall the primary muscles responsible for eye movements.

**Correct Answer: C. Superior Oblique muscle**