What action does the superior rectus perform when functioning?

The superior rectus muscle is primarily responsible for elevating the eye, which means it moves the eye upward. Additionally, it also has an adducting function, meaning it can draw the eye slightly inward toward the nose when the eye is elevated. This combination of elevating and adducting allows the superior rectus to facilitate upward and inward movement of the eye, making choice C the correct description of its actions.

The other options do not accurately reflect the primary functions of the superior rectus. Abducting the eye refers to moving it outward away from the midline, which is not a function of this muscle. Adducting alone would indicate moving the eye inward without elevation, and depressing the eye refers to downward movement, functions associated with different eye muscles, particularly the inferior rectus.