Final answer:
The correct answer is: a) Head, shaft. The head of the vertebral end articulates with the thoracic vertebrae, and the shaft is the flattened part of the structure.
Step-by-step explanation:
The vertebral end consists of the head, which articulates with one or two thoracic vertebral bodies, and a flattened shaft. Thoracic vertebrae are characterized by long, downward projecting spinous processes and facets on the vertebral body for rib attachment. This structure is vital for the articulation of the ribs with the spine, allowing for respiratory movement and stabilization of the thoracic cage.