Which of the following bones might refer to an injury of an arm bone?

The ulna is one of the two long bones in the forearm, positioned on the side opposite the thumb, and plays a crucial role in the structure and function of the arm. In the context of injuries, any trauma to the arm typically involves the ulna or the radius, which together enable a wide range of movements at the elbow and wrist.

The fibula, while a bone of the leg, does not pertain to arm injuries. The scapula is a bone of the shoulder girdle, which supports the arm but is not classified as an arm bone itself. The patella, commonly known as the kneecap, is situated in the leg and is unrelated to arm injuries. Therefore, when discussing potential injuries to an arm bone specifically, the ulna is the correct and relevant choice.