The primary function of the humerus bone in the appendicular skeleton is:

Correct Answer: C

Rationale: The humerus, an upper arm bone in the appendicular skeleton, facilitates arm movement by articulating with the scapula and forearm bones (radius, ulna). It doesn’t protect the heart (rib cage’s role) or support lower limbs, making 'Facilitating arm movement' the correct answer.

Correct Answer: A

Rationale: A joint, or articulation, is the anatomical location where two bones connect, allowing for stability or movement (e.g., knee, shoulder). Tendons connect muscles to bones, ligaments connect bones to other bones, and muscles move bones but aren’t the meeting point, making 'joint' the correct answer.

Correct Answer: D

Rationale: Short bones, like carpals and tarsals, have roughly equal length and width, providing stability and support. Flat bones are thin and broad, irregular bones have complex shapes, and long bones are longer than wide, making 'short' the correct classification.

Correct Answer: D

Rationale: Compact bone is organized into cylinder-shaped units called osteons (or Haversian systems—both terms are synonymous), containing lamellae and a central canal. Trabeculae are in spongy bone, not compact, so 'Both A and C are correct' reflects the interchangeable terminology.

Correct Answer: B

Rationale: Yellow bone marrow, found in the medullary cavity of adult long bones, is primarily fat tissue (adipose), serving as an energy reserve. Cartilage is at joints, and red/white blood cells are in red marrow, making 'fat tissue' correct.