3. In the sodium-potassium pump
(A) sodium is transported out of the cell and potassium into the cell, both against concentration gradients
(B) sodium is transported into the cell and potassium out of the cell, both against concentration gradients
(C) sodium is transported out of the cell and potassium into the cell, both in the same direction as concentration gradients
(D) sodium and potassium are both transported out of the cell against concentration gradients