Evidence for the Role of the Primary Motor Cortex Comes

Evidence for the role of the primary motor cortex comes from experiments that show that

A) activation of individual neurons of the motor cortex matches activation of individual muscles.
B) activation of individual neurons of the motor cortex matches activation of individual motor units.
C) activity of some neurons of the motor cortex correlates with the force or direction of a movement.
D) the number of motor cortex neurons that fire action potentials is linearly related to the force of the muscle contraction.