The sodium-potassium pump is primarily responsible for the

A) resting potential.
B) action potential.
C) excretion of salts.
D) contraction of muscle fibers.
E) maintenance of isotonic water balance.

The sodium-potassium pump is responsible for the resting potential, which is the electrical potential across the cell membrane when the cell is not actively transmitting impulses. The pump plays a crucial role in maintaining this potential by pumping sodium ions out of the cell and potassium ions into the cell, creating a concentration gradient that can be used to generate electrical impulses. Choices B, C, D, and E are not directly related to the function of the sodium-potassium pump.