What bones are referred to as forming the appendicular skeleton?

The appendicular skeleton is primarily composed of the bones that form the limbs and the girdles that connect them to the axial skeleton. This includes the bones of the arms and legs, as well as the shoulder blades (scapulae) and pelvic girdle. These structures are crucial for movement and mobility, supporting the body's appendages.

While the other choices refer to various components of the skeletal system, they do not accurately describe the appendicular skeleton. The skull and spine make up part of the axial skeleton, which provides central support and protection for the brain and spinal cord. The pelvis and ribcage also belong to the axial skeleton, serving protective and supportive functions for the upper body. The vertebral column is similarly part of the axial skeleton, providing structural integrity and support for the body. Thus, the choice that correctly identifies the elements forming the appendicular skeleton is the one that focuses solely on the limb bones.