## Core Concept
The posterior longitudinal ligament (PLL) is a significant structure in the spine, providing stability and protection to the vertebral column. It runs along the posterior aspect of the vertebral bodies, within the spinal canal, and plays a crucial role in limiting spinal extension. Anatomically, it is continuous with other structures at specific points.

## Why the Correct Answer is Right
The posterior longitudinal ligament continues as the membrana tectoria (or tectorial membrane) superiorly. The membrana tectoria is a fibrous band that is considered a superior extension of the posterior longitudinal ligament. It is located in the upper part of the spine and attaches to the posterior aspect of the body of the axis (C2) and the superior margin of the foramen magnum of the occipital bone. This continuation provides a strong ligamentous connection between the axis, the occipital bone, and by extension, the posterior longitudinal ligament and the cranial structures.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because it does not accurately represent the continuation of the posterior longitudinal ligament.
- **Option B:** This option is incorrect as it does not correctly identify the structure that the posterior longitudinal ligament continues as.
- **Option C:** Although not directly provided, any other option not stating "membrana tectoria" would be incorrect based on the accurate anatomical continuation.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the posterior longitudinal ligament is crucial for spinal stability, and its injury can lead to significant spinal instability. The continuation of the PLL as the membrana tectoria highlights the integrated nature of the ligamentous system supporting the spine and cranium.

## Correct Answer Line
**Correct Answer: B. membrana tectoria.**