The Relative Concentrations of Na⁺ and K⁺ Remain Constant During

Multiple Choice

The relative concentrations of Na⁺ and K⁺ remain constant during a single action potential,despite movement of these ions across the membrane,because

A) they cross back immediately through recovery channels.
B) they are pumped back across using the Na⁺/K⁺ ATPase pump.
C) they are forced back across the membrane as the action potential moves away.
D) the refractory periods do not end until all ions have been returned to their original areas.