Final answer:
The biceps brachii is the muscle that flexes and supinates the arm at the elbow; the brachialis helps in flexing the forearm, and the triceps brachii extends the forearm. The correct option is D) Biceps brachii
Step-by-step explanation:
The muscles responsible for the flexion and/or supination of the arm at the elbow are the biceps brachii, brachialis, and brachioradialis.
Specifically, the biceps brachii is a two-headed muscle that crosses both the shoulder and elbow joints to flex the forearm and assists in supination at the radioulnar joints as well as flexing the arm at the shoulder joint.
The brachialis muscle is located deep in the biceps brachii and supplies additional power in flexing the forearm. Regarding the question, it would be the biceps brachii (D) that flexes and supinates the arm at the elbow. In contrast, the triceps brachii muscle extends the forearm. The correct option is D) Biceps brachii