**Core Concept**
Radical neck dissection is a surgical procedure used to remove lymph nodes and other tissues in the neck that contain cancer. The goal of this procedure is to remove all cancerous tissue while preserving as much normal tissue as possible.

**Why the Correct Answer is Right**
In a radical neck dissection, the structures that are typically preserved include the sternocleidomastoid muscle, the spinal accessory nerve, and the internal jugular vein. The sternocleidomastoid muscle is a key muscle in the neck that helps to rotate the head and flex the neck. The spinal accessory nerve is responsible for innervating this muscle and is also involved in the control of other neck muscles. The internal jugular vein is a major vein that returns blood from the head and neck to the heart.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify which structure is preserved. In a radical neck dissection, multiple structures are preserved, but the question asks for a specific one.
* **Option B:** This option is incorrect because the submandibular gland is often removed during a radical neck dissection, especially if it is involved with cancer.
* **Option C:** This option is incorrect because the omohyoid muscle is often divided or removed during a radical neck dissection, rather than being preserved.

**Clinical Pearl / High-Yield Fact**
One key aspect of a radical neck dissection is the preservation of the spinal accessory nerve to prevent shoulder dysfunction, known as "frozen shoulder" or fibrositis.

**Correct Answer:** C.