Compact bone differs from spongy (cancellous) bone because compact bone:

Correct Answer: D

Rationale: Compact bone has osteons with Haversian canals for vessels, unlike spongy bone’s trabeculae. Both have marrow, short bones vary. Answer is D, per the document.

Correct Answer: C

Rationale: The acetabulum, a socket in the pelvis (coxal bone), articulates with the femur. Not occipital, humerus, or tibia. Answer is C, per the document.

Correct Answer: C

Rationale: A foramen is a hole in a bone (e.g., foramen magnum) for nerves/vessels, not a depression, roughening, or projection. Answer is C, per the document.

Correct Answer: C

Rationale: The rib cage (ribs, sternum, thoracic vertebrae) primarily protects the heart and lungs in the thoracic cavity. Stomach is abdominal, spinal cord is within vertebrae, and lungs attach via pleura—not the rib cage’s purpose. 'Protect the heart and lungs' is correct.

Correct Answer: B

Rationale: Muscles move bones by pulling via tendons when they contract; they can’t push (bones provide push via leverage). Automatic isn’t a mechanism, making 'pull movement only' correct.