Final answer:
The true statement as the membrane potential moves farther away from the equilibrium potential is that the ionic current is reduced. This effect is due to alterations in the electrochemical gradient forces that govern ion movements across the membrane, pertaining to depolarization and repolarization states.
Step-by-step explanation:
When the membrane potential moves farther away from the equilibrium potential, option (c) is true: the ionic current is reduced. This happens because there are two forces that drive the diffusion of ions across the plasma membrane—an electrical force and a chemical force, known as the electrochemical gradient. As the membrane potential moves away from this equilibrium potential, the forces that drive ion movement across the cell membrane are altered, which typically conflates with reduced ionic current moving across the membrane.
Specifically, because the concentration of Na+ ions is higher outside of the cell, an influx would lead to depolarization, hence making the inside of the membrane less negative. If K+ ions were to leave the cell, it would lead to repolarization, making the inside of the cell more negative as the membrane potential moves back toward the resting potential.