Read the following statements.

Statement I: Rapid influx of ${\mathrm{Na}}^{+}$ causes depolarisation of the axonal membrane and the subsequent repolarisation is caused due to efflux of ${\mathrm{K}}^{+}$.

Statement II: The ionic gradients across the resting axonal membrane are maintained by the active transport of ions by the sodium - potassium pump.

In the light of given statements, choose the correct answer from the options given below.