Use the Following to Answer Questions

Multiple Choice

Use the following to answer questions :

-Which of the following factors best explains the cause of the onset of a period where the neuron shown will not fire?

A) The channels at the region labeled 3 are closed.
B) The sodium ions at the region labeled 3 are depleted.
C) The channels at the region labeled 4 are open.
D) The sodium ions at the region labeled 4 are replenished.