## **Core Concept**
The question tests knowledge of muscles that control scapular movement. Scapular retraction is a posterior movement of the scapula, bringing it closer to the spine. This movement is crucial for various actions, including pushing and rowing.

## **Why the Correct Answer is Right**
The **Trapezius muscle**, specifically its middle and lower fibers, plays a significant role in scapular retraction. When the trapezius contracts, it helps pull the scapula towards the spine, thereby causing retraction. This muscle works in coordination with the **Rhomboids** to achieve this movement. The trapezius muscle is innervated by the cranial nerve XI (spinal accessory nerve) and is a key muscle in movements of the scapula.

## **Why Each Wrong Option is Incorrect**
- **Option A:** The **Pectoralis major** is involved in movements of the shoulder joint, such as flexion, extension, and adduction of the arm, but not in scapular retraction.
- **Option B:** The **Levator scapulae** does assist in elevating the scapula and rotating it downward but is not the primary muscle for scapular retraction.
- **Option D:** The **Serratus anterior** primarily functions to rotate the scapula upward and forward (protraction), which is the opposite of retraction.

## **Clinical Pearl / High-Yield Fact**
A useful clinical correlation to remember is that weakness of the **Trapezius muscle** can lead to a drooping shoulder or a winged scapula appearance, especially when pushing against resistance. This is a key point for physical medicine and rehabilitation exams.

## **Correct Answer:** C. Trapezius.