**Core Concept**
The ligamentum denticulatum, also known as the denticulate ligament, is a series of ligaments that connects the pia mater to the dura mater in the spinal cord. It helps to anchor the spinal cord and provides a pathway for the spinal nerves.

**Why the Correct Answer is Right**
The lowest projection of the ligamentum denticulatum is found at the level where the spinal cord terminates, which is typically around the L1-L2 vertebral level. This is because the spinal cord ends before the vertebral column, and the denticulate ligaments extend from the pia mater to the dura mater, providing support and anchorage to the spinal cord. The precise termination of the spinal cord varies slightly between individuals, but the L1-L2 level is generally accepted as the lowest point.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not a valid option.
* **Option B:** Not a valid option.
* **Option C:** Not a valid option.

**Clinical Pearl / High-Yield Fact**
The ligamentum denticulatum is an important anatomical structure to recognize in the context of spinal cord injuries or surgeries, as it can be damaged or torn, leading to potential complications.

**Correct Answer:** C. L1-L2.