Which bones are classified as part of the appendicular skeleton’s lower section?

The bones that make up the appendicular skeleton's lower section include the pelvic girdle, which consists of the hip bones (ilium, ischium, and pubis) and plays a crucial role in supporting the weight of the upper body when standing and transferring that weight to the lower limbs during movement. The pelvic girdle also provides attachment points for the lower limbs and helps protect the organs located in the pelvic area.

The other options pertain to different parts of the skeletal system. The cervical and thoracic vertebrae are part of the axial skeleton, which protects the brain and spinal cord, and supports the head and trunk. The sacrum, while located in the pelvic region, is also classified within the axial skeleton as it connects with the vertebral column. Thus, the pelvic girdle is the only structure listed that is specifically classified as part of the appendicular skeleton's lower section.