If K⁺ Can Exit the Cell Through Leak Channels, Why

If K⁺ can exit the cell through leak channels, why don't they flow out until there are equal concentrations on both sides of the membrane?

A) K⁺ can act as an enzymatic cofactor, and most K⁺ ions are bound to cellular enzymes.
B) The leak channels allow a very slow leak that cannot keep pace with active import of K⁺ ions.
C) Chelator molecules trap K⁺ on the inside of the membrane.
D) The negative electrical potential inside the cell creates a force that holds the K⁺ ions in.