**Core Concept**
The **extraocular muscles** control eye movements, with each muscle having a primary action. The **superior rectus** is one of these muscles, responsible for elevating the eyeball.

**Why the Correct Answer is Right**
The **superior rectus** muscle primarily acts to **elevate** the eyeball, allowing us to look upwards. This action is crucial for activities such as reading signs or looking at objects above the horizon. The muscle is innervated by the **oculomotor nerve (CN III)**, which coordinates its movements.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not accurately describe the primary action of the **superior rectus**.
**Option B:** Incorrect as it is not the primary function of the **superior rectus**.
**Option C:** Incorrect because the **superior rectus** does not primarily rotate the eyeball.

**Clinical Pearl / High-Yield Fact**
Remember that the **superior rectus** also has secondary actions, including **adduction** and **intorsion** of the eyeball, which are important in clinical examinations of eye movements.

**Correct Answer:** **Correct Answer: B. Elevation.**