**Core Concept**
The spinal cord is surrounded by the dura mater, a thick, fibrous membrane, and the vertebral bodies. In the event of a crush injury or swelling of the spinal cord, the space between the dura and the vertebral bodies can become compromised, trapping a critical structure.

**Why the Correct Answer is Right**
The structure that would be trapped between the dura and the vertebral body is the **arachnoid mater**. This is because the arachnoid mater is a delicate membrane that lies between the dura mater and the pia mater, which directly adheres to the spinal cord. As the spinal cord swells, the space between the dura and the vertebral body narrows, compressing the arachnoid mater and preventing it from expanding with the cord.

**Why Each Wrong Option is Incorrect**
* **Option A:** The spinal cord itself would not be trapped between the dura and the vertebral body, as it is directly adhered to the pia mater.
* **Option B:** The pia mater is the membrane that directly adheres to the spinal cord and would not be trapped between the dura and the vertebral body.
* **Option D:** The epidural space, which lies between the dura mater and the vertebral bodies, would not be trapped as it is a potential space that can expand with swelling.

**Clinical Pearl / High-Yield Fact**
The arachnoid mater is a critical structure that can become compressed or trapped in cases of spinal cord swelling, leading to increased intracranial pressure and potentially life-threatening complications.

**Correct Answer:** C.