The prime mover of wrist extension is the .

The primary muscles involved in wrist extension, which act on the wrist only, are the extensor carpi radialis longus, extensor carpi radialis brevis and the extensor carpi ulnaris. All of these muscles need to be fired simultaneously to avoid any radial or ulnar deviation with extension.

its b i just took the test and i hit a it was wrong

the answer is d its the most logical and accurate out of them all : )