The primary function of the pelvic girdle in the appendicular skeleton is:

Correct Answer: C

Rationale: The pelvic girdle, part of the appendicular skeleton, supports the lower limbs (via hip joints) and protects pelvic organs (e.g., bladder). It does not protect the spinal cord (vertebral column’s role) or aid respiration, making 'Supporting the lower limbs and organs' the correct answer.

Correct Answer: C

Rationale: Myoglobin, a protein in muscle cells, binds and stores oxygen, releasing it for aerobic respiration during contraction when oxygen demand rises. ATP and creatine phosphate provide energy, while troponin regulates contraction, making 'Myoglobin' the correct answer.

Correct Answer: C

Rationale: The ribs, part of the thoracic cage in the axial skeleton, form a protective enclosure around vital organs. The 12 pairs of ribs, along with the sternum and thoracic vertebrae, shield the heart and lungs directly. The liver, located below the diaphragm, is partially protected by the lower ribs. Vertebrae protect the spinal cord, the skull protects the brain, and the femur is a leg bone, making 'ribs' the correct answer.

Correct Answer: B

Rationale: The skeleton protects soft organs (e.g., skull protects brain), supports the body (via structure), and stores minerals (calcium, phosphorus) and fat (yellow marrow). Vitamin D production occurs in the skin upon sunlight exposure, not the skeleton, though bones use vitamin D to absorb calcium. Thus, 'produces vitamin D' is NOT a skeletal function.

Correct Answer: A

Rationale: The epiphyses of long bones are covered with articular (hyaline) cartilage at joints, reducing friction and protecting bone ends during movement. Red and yellow marrow are inside bones, and the endosteum lines the medullary cavity, making 'articular (hyaline) cartilage' correct.