9. The critical function of the sodium-potassium pump of neurons is to move
(A) Na+ and K+ into the cell.
(B) Na^{+ and K+ out of the cell.
(C)Na+ into the cell and K+ out of the cell.
(D) Na+ out of the cell and K+ into the cell.
(E) Na+ and K+ into the cell and H+ out of the cell through an antiport mechanism.}