Final answer:
The most commonly broken arm bone in the forearm is the radius (a), which is susceptible to a Colles fracture, especially from falls onto an outstretched hand.
Step-by-step explanation:
The direct answer to the question is: a) Radius.The radius is the bone found on the lateral side of the forearm and is involved in forms of articulation with the wrist and elbow. It is prone to a specific fracture type known as a Colles fracture which occurs at the distal end of the radius around the wrist. This type of fracture is characterized as the most common forearm fracture and often results from a fall onto an outstretched hand, leading to the breakage of the larger bone of the forearm. The radius, along with the ulna, forms the structure of the forearm and enables a wide range of movements including rotation.
The femur is the longest and strongest bone in the body but is not found in the forearm. The patella, commonly referred to as the kneecap, is a small bone located at the knee, and the tibia is the shinbone, neither of which are forearm bones. Therefore, options b, c, and d are not correct in the context of the most commonly broken arm bone.