Final answer:
The axial skeleton includes the skull, vertebral column, and thoracic cage. It forms the central axis of the body and supports various functions including posture and protection.
Step-by-step explanation:
The question refers to the composition of the axial skeleton. Among the listed options, the axial skeleton includes the skull, vertebral column (spine), and thoracic cage (formed by the ribs and sternum). This structure forms the central axis of the human body and supports the head, neck, back, and chest. It is critical for maintaining upright posture, transmitting weight, and protecting internal organs. The correct answer to the question is option a) thoracic cage and vertebral column.