**Core Concept**
The inferior angle of the scapula serves as a significant anatomical landmark, particularly in clinical settings where it is used to estimate the level of the spinal column. This concept is crucial in orthopedic, neurosurgical, and emergency medical procedures.

**Why the Correct Answer is Right**
The inferior angle of the scapula is typically at the level of the seventh thoracic vertebra (T7). This is because the scapula is positioned in such a way that its inferior angle aligns with the spinous process of T7. This alignment is due to the way the scapula is fixed to the thoracic cage through the scapulothoracic joint. When the scapula is positioned in its normal anatomical position, the inferior angle is usually at the level of T7, making it a reliable landmark for clinical purposes.

**Why Each Wrong Option is Incorrect**
**Option A:** T4 is too high, as the superior border of the scapula typically lies at the level of T2-T3, not T4.
**Option B:** T5 is closer, but still too high, as the inferior angle of the scapula is positioned more caudally.
**Option C:** T6 is also incorrect, as the inferior angle of the scapula is typically positioned at the level of T7, not T6.

**Clinical Pearl / High-Yield Fact**
When assessing the level of the spine, the inferior angle of the scapula can be used as a quick and reliable landmark. However, it is essential to remember that this landmark can be affected by scapular rotation or other anatomical variations.

**✓ Correct Answer: D. T7**