18. During the propagate ion of a nerve ion of a nerve impulse, the action potential results from the movement of(A) K⁺ ions from intracellular fluid to extracellular fluid(B) K⁺ ios from extracellular fluid to intracellular fluid(C) Na⁺ ions from extracellular fluid to intracellular fluid(D) Na⁺ ions from intracellular fluid to extracellular fluid