**Core Concept**
The question is testing the understanding of extraocular muscle functions, specifically the movements of the eyeball. The correct answer involves identifying the muscles responsible for downward rotation, medial rotation, and extorsion of the eyeball.

**Why the Correct Answer is Right**
The correct answer involves the action of the inferior oblique muscle. The inferior oblique muscle is responsible for the following movements:
- Downward rotation (intorsion) of the eyeball
- Medial rotation of the eyeball
- Extorsion of the eyeball
The inferior oblique muscle is innervated by the third cranial nerve (oculomotor nerve) and plays a crucial role in the movement of the eyeball.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not involve the muscles responsible for the specified movements.
**Option B:** This option is incorrect because it is not the primary muscle responsible for downward rotation, medial rotation, and extorsion of the eyeball.
**Option C:** This option is incorrect because it involves muscles that are primarily responsible for upward rotation (suppression) and lateral rotation of the eyeball.

**Clinical Pearl / High-Yield Fact**
The inferior oblique muscle is the most horizontal of all the extraocular muscles and is responsible for the majority of the extorsion movement of the eyeball.

**Correct Answer:** C. Superior oblique