Final answer:
The transverse foramen d) is a bone feature found only on cervical vertebrae and is a unique characteristic that distinguishes them from other vertebrae such as those in the thoracic and lumbar regions.
Step-by-step explanation:
The bone feature that is found only on cervical vertebrae is a transverse foramen. This is a distinctive trait of cervical vertebrae, which are bones in the neck portion of the spine. Cervical vertebrae, such as the typical axis (C2 vertebra) and atlas (C1 vertebra), have small bodies and unique characteristics. The atlas does not have a typical vertebral body or spinous process but is formed by bony rings and elongated transverse processes. The axis features an upward projecting dens for articulation with the atlas. Unlike cervical vertebrae, thoracic vertebrae have long, downward-projecting spinous processes for rib articulation, and lumbar vertebrae, which support the greatest body weight, have a large, thick body and a short, blunt spinous process.