Final answer:
The most distal location on the humerus is the trochlea, which is a part of the distal humerus involved in articulating with the ulna at the elbow.
Step-by-step explanation:
The structure most distal on the humerus would refer to the part that is furthest from the shoulder joint, closer to the elbow and the hand. According to the information provided, the structures listed on the humerus are the trochlea, greater tubercle, deltoid tuberosity, medial epicondyle, and anatomical neck.
The trochlea of the humerus is part of the distal humerus that articulates with the ulna, making it more distal compared to the other options. Structures like the greater tubercle and the deltoid tuberosity are found on the proximal end and the shaft of the humerus, respectively, whereas the medial epicondyle, although also part of the distal humerus, is not as distal as the trochlea. Therefore, the answer is a. trochlea, which is the most distal structure among those listed.