Which bone serves as the supporting structure of the upper arm?

The humerus is the bone that serves as the supporting structure of the upper arm. It is the longest bone in the arm and extends from the shoulder to the elbow. The humerus plays a critical role in arm movement and stability, allowing for a wide range of motions at the shoulder joint while providing support to the entire upper limb.

The other options refer to different bones that have distinct roles in the skeletal structure. The clavicle, or collarbone, connects the arm to the body and provides some support but is not the primary bone of the upper arm. The radius and ulna are located in the forearm, functioning primarily in wrist and elbow movements but not in supporting the upper arm itself. The scapula, or shoulder blade, is involved in shoulder mobility and stability but does not constitute the arm's structure.