Final answer:
The radius is the forearm bone that allows for rotation of the hand around the arm's longitudinal axis, not the ulna, humerus, or carpals.
Step-by-step explanation:
The bone in the forearm that enables rotation of the hand around the longitudinal axis of the arm is the radius.
The forearm consists of two bones, the ulna and the radius. The radius is located along the lateral (thumb) side of the forearm and articulates with the humerus at the elbow. It is responsible for rotating the hand to perform tasks such as turning a doorknob or using a screwdriver.
The forearm bone that enables the rotation of the hand around the longitudinal axis of the arm is the radius. The radius is located on the lateral (thumb) side of the forearm and permits the motion known as pronation and supination. This is in contrast to the ulna, which is positioned on the medial side of the forearm and does not play a significant role in the hand's rotation. The humerus is involved in articulating with the ulna and radius at the elbow but does not facilitate the rotational motion of the hand itself. The carpals are the bones of the wrist and do not directly enable the rotation of the hand.