The first event to occur when an adequate stimulus is applied to a neuron is

Through my research I found questions similar to this with matching choices and they are the following: 

A)the membrane potential moves immediately to + 30m V
B)the potassium channels open
C)the sodium channels are inactivated
D)some of the sodium channels at the point of stimulation open

Among those choices, the best answer would be D) Some of the sodium channels at the point of stimulation open.

It is used to during sexual reproduction between humans