**Core Concept**
Radical neck dissection (RND) is a surgical procedure that involves the removal of lymph nodes and other structures in the neck to treat or prevent the spread of cancer. The goal of RND is to remove all the lymph nodes and tissues that are at risk of containing cancer cells, while preserving the function of the surrounding tissues and nerves.

**Why the Correct Answer is Right**
In a RND dissection, the following structures are typically removed: sternocleidomastoid muscle (Option A), internal jugular vein (Option B), and spinal accessory nerve (Option C). These structures are removed to ensure that all the lymph nodes and tissues at risk of containing cancer cells are removed.

**Why Each Wrong Option is Incorrect**
* **Option A:** The sternocleidomastoid muscle is typically removed in a RND dissection to allow for complete removal of lymph nodes in the neck.
* **Option B:** The internal jugular vein is also removed in a RND dissection to ensure complete removal of lymph nodes and tissues at risk of containing cancer cells.
* **Option C:** The spinal accessory nerve is typically sacrificed in a RND dissection, as it is often in close proximity to the lymph nodes that are being removed.

**Clinical Pearl / High-Yield Fact**
It is essential for surgeons to carefully identify and preserve the accessory nerve during RND dissection, as damage to this nerve can result in significant morbidity, including shoulder dysfunction and weakness.

**Correct Answer: D. The Common Carotid Artery**