Final answer:
A resting neuron under the influence of a neurotransmitter that opens K+ channels will hyperpolarize and return to its resting membrane potential.
Step-by-step explanation:
A resting neuron under the influence of a neurotransmitter that opens K+ channels will hyperpolarize and return to its resting membrane potential by allowing K+ ions to leave the cell. When the K+ channels open, the diffusion of K+ out of the cell makes the membrane potential more negative than its normal resting potential.
This occurs during the refractory period, when the sodium channels are closed and cannot open. Once the extra K+ ions diffuse out of the cell, the neuron returns to its resting state.