Final answer:
The ion responsible for repolarization of a neuron during an action potential is Potassium (K+), as it flows out of the neuron to restore the resting membrane potential. Option c.
Step-by-step explanation:
The ion responsible for repolarization of a neuron during an action potential is Potassium (K+). During an action potential, after the initial depolarization due to an influx of sodium ions (Na+), repolarization occurs when the cell membrane becomes less permeable to Na+ and potassium channels open, allowing K+ to flow out of the neuron. This outflow of positive ions helps to restore the resting membrane potential of the neuron, making the interior of the neuron more negative relative to the outside once again.
Potassium's role in establishing the resting membrane potential and in restoring it after an action potential is critical. Without the movement of K+ ions out of the cell during repolarization, the neuron would not be able to return to its resting state and be ready to fire another action potential. Voltage-gated ion channels facilitate these processes, and designs such as the sodium-potassium pump help maintain the concentration differences essential for the neuron's electrical activity.