**Core Concept**
The sternocleidomastoid muscle is a complex structure in the neck, consisting of two parts: the sternal head and the clavicular head. The blood supply to this muscle is crucial for its function and is provided by branches of the cervical and thyrocervical arteries.

**Why the Correct Answer is Right**
The sternocleidomastoid muscle is primarily supplied by the superior and deep branches of the transverse cervical artery, which is a branch of the thyrocervical trunk. Additionally, the sternocleidomastoid muscle receives a direct branch from the occipital artery, which is a branch of the external carotid artery. The transverse cervical artery and the occipital artery provide a rich blood supply to the sternocleidomastoid muscle.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as the sternocleidomastoid muscle is not supplied by the inferior thyroid artery, which primarily supplies the thyroid gland and the parathyroid glands.
**Option B:** This option is incorrect as the sternocleidomastoid muscle is not supplied by the vertebral artery, which primarily supplies the vertebrae, the spinal cord, and the posterior cervical muscles.

**Clinical Pearl / High-Yield Fact**
The sternocleidomastoid muscle is a key structure in the neck, and its blood supply is crucial for its function. The transverse cervical artery and the occipital artery are the primary blood vessels that supply the sternocleidomastoid muscle.

**Correct Answer:** C.