How Does the Cell Maintain a Higher Level of K⁺

How does the cell maintain a higher level of K⁺ than of Na⁺?

A) The Na⁺ leaks out into the surrounding extracellular fluid.
B) K⁺ is bound to sites inside the cell.
C) The body contains less total Na⁺ than K⁺, so Na⁺ is found at a low concentration inside the cell.
D) Na⁺ is actively transported out of the cell and K⁺ actively transported in the cell.
E) Much of the Na⁺ outside the cell is bound to protein, so that no Na+ gradient exists across the cell membrane.