Humerus connects shoulder and elbow with distinct joint types

Steps:

• Examine upper limb bones and their articulations.
• Identify ball-and-socket joint at shoulder: involves humerus head in scapula's glenoid cavity.
• Check distal end for hinge joint: humerus trochlea articulates with ulna at elbow.
• Rule out forearm and shoulder girdle bones lacking both joint types.

Why A is correct:

• The humerus proximal head forms a ball-and-socket joint with the scapula glenoid cavity, allowing multi-directional movement, while its distal trochlea creates a hinge joint with the ulna, permitting flexion-extension at the elbow.

Why the others are wrong:

• B. Scapula: Flat bone forming shoulder socket but no ball end or hinge joint.
• C. Radius: Hinge at elbow with humerus but pivot joint with ulna, no ball-and-socket.
• D. Ulna: Hinge at elbow with humerus but no ball-and-socket joint.

Final answer: A