Final answer:
Articular cartilage covers both the head of the humerus and the glenoid cavity in the glenohumeral joint, facilitating smooth movement and a wide range of motion.
Step-by-step explanation:
The student's question pertains to the structure that covers the head of the humerus and the glenoid cavity in the shoulder joint. The correct answer to this question is Option 4: Articular cartilage on both the humerus and the glenoid cavity.
Articular cartilage is a thin layer of smooth and strong hyaline cartilage that covers the surfaces of bones where they come together to form joints. In the shoulder joint, or the glenohumeral joint, this cartilage covers both the head of the humerus and the glenoid cavity of the scapula. This allows for the large range of motions characteristic of the shoulder due to the cartilage reducing friction and facilitating smooth movement.