As the options of the question are not provided and not found therefore on the basis of previous knowledge a attempt has been made to answer the question.
Answer:
The action potential is generated in the neurons as a result of the movement of two ions mainly sodium and potassium. When the sodium gated channels open then the sodium ion move inside the cell which increases the positive charge. This causes depolarization of the neuron.
Thus, the movement of sodium ions into the neuron causes depolarization of the neuron.