The Analogy Used in the Book Referred to the Axon

The analogy used in the book referred to the axon membrane asa "gatekeeper." This means that the membrane:

A) determines whether an action potential will "pass" through the axon.
B) controls the balance of positive and negative ions in the interior and the exterior of the axon.
C) operates in an "all-or-none" fashion, either opening to allow neurotransmitters to pass or not.
D) uses the nodes of Ranvier to allow some ions to move out of the axon and neurotransmitters to move into the axon.