Why Are Action Potentials Usually Conducted in Only One Direction

Multiple Choice

Why are action potentials usually conducted in only one direction along an axon?

A) The nodes of Ranvier can conduct potentials in only one direction.
B) The brief refractory period prevents reopening of voltage-gated Na+ channels.
C) The axon hillock has a higher membrane potential than the terminals of the axon.
D) Ions can flow along the axon in only one direction.
E) Voltage-gated channels for both Na+ and K+ open in only one direction.