When the membrane is at rest, what are the forces acting on potassium ions?

A. Both the concentration gradient and the electrical gradient tend to move potassium ions into the cell.

B. Both the concentration gradient and the electrical gradient tend to move potassium ions out of the cell.

C. The concentration gradient tends to move potassium ions into the cell, and the electrical gradient tends to move them out of the cell.

D. The concentration gradient tends to move potassium ions out of the cell, and the electrical gradient tends to move them into the cell.