Which statement applies only to the axial skeleton, not the appendicular skeleton? A. It contains a pivot joint. B. It has muscles attached that work in pairs. C. It contains red bone marrow. D. It possesses fossa for bone articulation. E. It protects the heart and lungs.

The statement that applies only to the axial skeleton, not the appendicular skeleton is E. "It protects the heart and lungs."

Here's why:

A. Pivot joints are found in both the axial and appendicular skeleton. For example, the joint between the first and second vertebrae (axial) and the joint between the radius and ulna (appendicular).

B. Muscles work in pairs throughout the entire body, not just the axial skeleton. This is a basic principle of how muscles work, known as agonist and antagonist muscles.

C. Red bone marrow is found in various locations throughout the body, including bones of both the axial and appendicular skeleton. In adults, red marrow is often found in the skull, ribs, vertebrae, and pelvis (axial) and the ends of long bones like the femur and humerus (appendicular).

D. Fossae for bone articulation, or joints, are found throughout the body, not just in the axial skeleton.

E. The axial skeleton, which includes the skull, vertebral column, and rib cage, does indeed protect vital organs like the heart and lungs. The appendicular skeleton, which includes the limbs and girdles, does not have this function.