Question

the area of the motor cortex that is devoted to a particular region of the body is proportional to the
o size of the nerves that serve the area of the body.
o number of sensory receptors in the area of the body.
o size of the body area.
o number of motor units in that region.
o distance of the body area from the brain.

Explanation:

The motor cortex area for a body region relates to motor control. Motor units (a motor neuron and the muscle fibers it innervates) are key for movement. Nerves size (not main factor), sensory receptors (for sensation, not motor cortex's motor - focus), body area size (e.g., face has more motor cortex than large torso), and distance from brain (not relevant) are incorrect.

Answer:

number of motor units in that region.