Why Is an Action Potential Propagated Down an Unmyelinated Neuron

Multiple Choice

Why is an action potential propagated down an unmyelinated neuron plasma membrane?

A) because the action potential stimulates voltage-gated Cl^- channels adjacent to it
B) because the action potential stimulates voltage-gated Ca²⁺ channels adjacent to it
C) because the action potential stimulates voltage-gated Mg⁺ channels adjacent to it
D) because the action potential stimulates voltage-gated Na⁺ channels adjacent to it