Which muscle covers most of the posterior aspects of the humerus?

The triceps brachii is the correct answer because it is the primary muscle located on the posterior aspect of the humerus. This muscle consists of three heads (long, lateral, and medial) that converge into a single tendon at the elbow, allowing it to function primarily as an extensor of the forearm at the elbow joint. Its position allows it to dominate the back of the upper arm and cover a significant portion of the humeral shaft, making it critical for movements that involve extension, such as pushing.

In contrast, the quadriceps are a group of muscles located at the front of the thigh and are primarily involved in knee extension. The hamstrings are also located in the posterior part of the thigh and are responsible for knee flexion. The biceps brachii, situated on the anterior aspect of the upper arm, primarily facilitates elbow flexion and supination of the forearm. Thus, their anatomical locations and primary functions are not associated with the posterior aspects of the humerus, reinforcing why the triceps brachii stands out as the correct answer.