The is the difference in charge between the intracellular and extracellular space of a neuron. extracellular fluid intracellular fluid membrane potential resting potential

The answer to this question is membrane potential 

The gradient of electrolyte concentration from inside cell and outside cell will determine the membrane potential. Natrium or sodium is much higher outside the cell than inside cell. In contrast to the sodium, potassium is much more inside cells. This two electrolyte have major role in the membrane potential and action potential. 

Ithink the answer is c. i’m not sure though i’ll notify you when i have an exact answer!