The radius connects to many muscles, such as the biceps, supinator, flexor digitorum superficialis, flexor pollicis longus muscles, extensor ossis metacarpi pollicis, extensor primi internodii pollicis and the pronator teres muscles Furthermore, the radius is found on each arm thus contributing a total of two bones to the human body skeleton. http://www.learnbones.com/arm-bones-anatomy/
In archery, it is important to keep your shoulders in line. In picture A, the individual would have a difficult time aiming because they are using their muscles to hold the bow. I realize that you use muscles to hold the bow, but in picture B, the individual is using the bones in their arm to hold the pressure of the bow, allowing for a steadier aim.
The brachioradialis is a pear/tear shape which goes from the lateral part of the bicep (away from body) to the thumb). In conjunction with the other palm side muscle group (consisting of several muscle segments) and the bicep we see an intersection of three interlocking main shapes. Note the white areas showing the tendons (attaching muscle to bone)