**Core Concept**
The rhomboid major muscle is one of the muscles of the back, specifically part of the scapular stabilizers. It plays a crucial role in scapular rotation and upward movement, which is essential for various arm movements and maintaining proper posture.

**Why the Correct Answer is Right**
The rhomboid major muscle originates from the spinous processes of the thoracic vertebrae (T2-T5) and inserts on the medial border of the scapula. This insertion point is critical for its function, as it enables the muscle to pull the scapula upward and rotate it downward, contributing to the elevation of the arm and stabilization of the scapula during movements. The precise insertion point on the scapula allows for a mechanical advantage, enabling the muscle to generate the necessary force for its actions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as the rhomboid major does not originate from the cervical spine; its origin is from the thoracic vertebrae.
**Option B:** This option is incorrect as the rhomboid major does not insert on the lateral border of the scapula; it inserts on the medial border.
**Option C:** This option is incorrect as the rhomboid major does not insert on the superior angle of the scapula; its insertion is more medially located.

**Clinical Pearl / High-Yield Fact**
The rhomboid major muscle is often affected in individuals with poor posture or those who perform repetitive movements that strain the back muscles. This can lead to muscle imbalances and exacerbate conditions such as scapular winging.

**Correct Answer: D. The medial border of the scapula.**