The proximal end of the ulna illustrates the relationship of form and function. the rounded trochlear notch articulates with the hourglass shape of the trochlea. this forms a joint that allows for the hinge like motion of the forearm the rotational motion of the forearm the curling of the fingers the hyper extension of the forearm

Option A, The hinge like motion of the forearm

Explanation:

A hinge joint  allows for two motions at a time

a) Flexion - The bending motion

b) Extension - The strengthening motion of arm bones

At the  proximal end , the Ulna forms a joint with the humerus  and radius of forearm. The Ulna extends to form olecranon (the tip of the elbow) Both Ulna and radius bones are attached with an interosseous membrane that causes movement just like a hinge joint.

Option A is correct