Question

depolarization of a cell membrane occurs because
multiple choice
more sodium ions diffuse into the cell than potassium ions diffuse out of it
the concentration of sodium and potassium ions in the cell is at equilibrium
sodium ions are blocked from entering the cell
the concentration of sodium and potassium ions in the extracellular fluid is at equilibrium

Explanation:

Depolarization of a cell membrane occurs when the membrane potential becomes less negative. This is due to the influx of positively - charged sodium ions ($Na^+$) into the cell. More sodium ions diffuse into the cell than potassium ions ($K^+$) diffuse out, changing the charge distribution across the membrane.

Answer:

More sodium ions diffuse into the cell than potassium ions diffuse out of it