Final answer:
The muscles responsible for forearm supination are the biceps brachii and the supinator; the biceps brachii assists in supination during forearm flexion, while the supinator is specifically specialized for this motion.
Step-by-step explanation:
Among the options presented, the muscles that perform forearm supination are the biceps brachii and the supinator muscle. The biceps brachii is a two-headed muscle that crosses the shoulder and elbow joints to flex the forearm and it also plays a role in the supination of the forearm at the radioulnar joints.
The supinator muscle, as its name suggests, is specialized for the supination of the forearm, which is the motion that turns the forearm anteriorly, such that the palm faces upward or forward in anatomical position.