Which of the following contribute to the resting membrane potential of an axon?(a)     High concentration of Na+ in the ECF(b)    Negatively charged proteins in the axoplasm(c)     Sodium-potassium pump

The resting membrane potential arises from three major factors: (1) Unequal distribution of ions in the ECF and axoplasm (2) Inability of most anions (e.g., proteins) to leave the cell. (3) The sodium-potassium pumps. The sodium-potassium pumps contribute to the negativity of the resting membrane potential since these pumps remove more positive charges from the cell than they bring into the cell