**Core Concept**
The common carotid artery bifurcation is an essential anatomical landmark, and its location is crucial for understanding the vascular supply to the head and neck. This bifurcation gives rise to the internal and external carotid arteries. The **thyroid cartilage** serves as a key reference point for this bifurcation.

**Why the Correct Answer is Right**
The common carotid artery typically bifurcates at the upper border of the **thyroid cartilage**, which is usually around the level of the fourth cervical vertebra (C4). This location is critical for surgical and clinical procedures, including carotid endarterectomy and the assessment of carotid pulses.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the bifurcation is not typically located at the lower border.
**Option C:** This is also incorrect as it does not accurately describe the usual location of the bifurcation.
**Option D:** Similarly, this option does not correctly identify the bifurcation point.

**Clinical Pearl / High-Yield Fact**
Remembering that the common carotid bifurcation occurs at the upper border of the **thyroid cartilage** is vital for clinical exams and surgical planning. This knowledge helps in identifying potential sites for vascular access or pathology.

**Correct Answer:** C. Upper border of thyroid cartilage