Answer:
The influx of sodium ions causes the depolarization in the resting cells.
Step-by-step explanation:
Resting cells has the membrane potential of -70 mV. Potassium ions are abundant in the resting cell.
The influx of sodium ions in the resting cells will increase the membrane potential from -70mV to 30mV. The cells will depolarize die to the influx of sodium ions and the cell inside environment will become more positive than outside environment of the cell.
Thus, the cells will depolarize by the influx of sodium ions.