Question

stimulation of a neuron that terminates in the superior region of the left postcentral gyrus would produce
a sensation in the right leg.
a muscle twitch in the right leg.
a muscle twitch in the lips.
a sensation in the lips.
both sensations and muscle twitches in the right leg.

Explanation:

The postcentral gyrus is the primary somatosensory area. Neurons in this region receive sensory information. Also, the body is represented contralaterally (left hemisphere represents right side of the body) and somatotopically (superior region represents lower - body parts like the leg). So, stimulation of a neuron terminating in the superior region of the left postcentral gyrus would lead to a sensation (since it's the sensory cortex, not the motor cortex which would cause muscle twitches) in the right leg.

Answer:

a sensation in the right leg.