In What Position Is the Brachioradialis Most Effective as a Flexor

In what position is the brachioradialis most effective as a flexor of the forearm at the elbow joint?

A) when the forearm is halfway between full pronation and full supination at the radioulnar joints
B) when the forearm is in full supination at the radioulnar joints
C) when the forearm is in full pronation at the radioulnar joints
D) none of the above;the amount of pronation/supination of the forearm at the radioulnar joints is irrelevant to the ability of the brachioradialis to perform flexion of the forearm at the elbow joint