What structure is described as a bony cage made up of the spine, thoracic vertebrae, sternum, and ribs?

The structure described as a bony cage made up of the spine, thoracic vertebrae, sternum, and ribs is known as the thorax. The thorax plays a crucial role in protecting vital organs, such as the heart and lungs, which are located within the thoracic cavity. This region provides not only structural support but also serves as an attachment point for muscles involved in respiration and maintaining posture.

The thorax is distinct from other anatomical structures included in the choices. The pelvis supports the lower body and houses reproductive and excretory organs. The skull protects the brain and forms the structure of the head. The vertebral column, while an essential part of the thoracic structure, primarily refers to the spine itself and does not encompass the ribs and sternum that collectively form the thorax. Thus, the thorax is the correct choice as it encapsulates all these components as a protective bony framework.