Which description is correct about the α motor neuron in anterior horn of the spinal cord.

A、finalcommonpathwayofthereflexivecontrolofskeletalmusclecontraction.;
B、bigαmotorneuroncomposethebigmotorunit.;
C、smallαmotorneuroncomposethesmallmotorunit.;
D、releaseglutamateatthepresynapticterminal.