What structure is formed by the 12 pairs of bones in the ribs?

The correct answer is thorax, which refers to the part of the body formed by the rib cage. This region is encased by the twelve pairs of ribs that connect to the thoracic vertebrae in the spine and the sternum at the front. The thorax serves as a protective framework for vital organs such as the heart and lungs, while also providing structural support for the upper body.

The vertebral column consists of the individual vertebrae that form the spine and does not specifically relate to the structure formed by the ribs. The sternum is a single bone to which the ribs connect at the front but does not constitute the entire structure formed by the ribs. The pectoral girdle, composed of the clavicles and scapulae, supports the upper limbs and is not directly involved in forming the rib cage. Thus, the thorax is the appropriate term for the full structure created by the ribs and the surrounding bones.