**Core Concept**
The parathyroid glands receive their blood supply from branches of the thyroid arteries, which are crucial for maintaining parathyroid function and hormone secretion. The thyroid arteries are closely associated with the thyroid gland and provide vital nutrients and oxygen to the parathyroid glands.

**Why the Correct Answer is Right**
The inferior thyroid artery is the primary supplier of the parathyroid glands. It is a branch of the thyrocervical trunk and gives rise to the superior and inferior parathyroid arteries, which supply the parathyroid glands. The parathyroid glands are embedded within the posterior surface of the thyroid gland and receive their blood supply from the thyroid arteries. The inferior thyroid artery is more closely associated with the inferior parathyroid glands, while the superior thyroid artery supplies the superior parathyroid glands.

**Why Each Wrong Option is Incorrect**
**Option A:** The thyrocervical trunk gives rise to the inferior thyroid artery, but it is not directly involved in supplying the parathyroid glands.
**Option B:** The costocervical trunk is a branch of the subclavian artery and does not supply the parathyroid glands.
**Option C:** The ascending cervical artery is a branch of the inferior thyroid artery, but it is not the primary supplier of the parathyroid glands.

**Clinical Pearl / High-Yield Fact**
The parathyroid glands are closely associated with the thyroid gland and receive their blood supply from branches of the thyroid arteries. The inferior thyroid artery is the primary supplier of the parathyroid glands, and damage to this artery can lead to parathyroid gland dysfunction.

**Correct Answer:** C. Inferior thyroid artery.