Which bone extends from the thumb side of the wrist to the elbow?

The radius is the correct answer because it is one of the two long bones of the forearm, extending from the elbow down to the wrist on the thumb side. Located parallel to the ulna, the radius plays a critical role in wrist movement and the rotational capabilities of the forearm. When the forearm is turned palm-up, the radius crosses over the ulna, demonstrating its functional relationship in arm mobility.

In contrast, the ulna is found on the opposite side of the forearm from the thumb, running parallel to the radius but extending from the elbow down to the wrist on the side of the little finger. The clavicle is the bone that connects the arm to the body, commonly known as the collarbone, and does not run from the wrist to the elbow. The sternum is the breastbone located in the center of the chest and has no relationship to the bones of the forearm. Thus, the radius is distinctly identified for its specific location and function in the anatomy of the arm.