The axial skeleton is composed of the

Step 1: Analyze the question The question asks which parts make up the axial skeleton, so we need to know how the skeleton is divided.

Step 2: The concept The vertebrate skeleton has two main divisions:

• Axial skeleton: forms the central axis (the main "trunk" line) of the body. It includes the skull, vertebral column, ribs, and sternum (breastbone). Its main jobs are protecting the brain, spinal cord, heart and lungs, and supporting the body.
• Appendicular skeleton: includes the limbs (arms and legs) and the girdles (pectoral/shoulder girdle and pelvic/hip girdle). It is mainly for movement.

Step 3: Check each option

• A. Skull and vertebral column: Both are core parts of the axial skeleton. ✔
• B. Limbs and girdles: These make up the appendicular skeleton. ✘
• C. Atlas and axis: These are only the first two cervical vertebrae, just a small part of the vertebral column, so they are not the full composition. ✘
• D. Radius and ulna: These are forearm bones, part of the appendicular skeleton. ✘

Step 4: Answer The axial skeleton is composed of the skull and vertebral column (along with the ribs and sternum), so the answer is A.

Exam tip: Remember "Axial = Axis of the body" (head and trunk), while "Appendicular = Appendages" (limbs and the girdles that attach them). If an option mentions limbs or girdles, it's appendicular.