Why Are Action Potentials Usually Conducted in One Direction

Multiple Choice

Why are action potentials usually conducted in one direction?

A) Ions can flow along the axon in only one direction.
B) Voltage-gated Na⁺ channels are inactivated during the refractory period.
C) The axon hillock has a higher membrane potential than the terminals of the axon.
D) Voltage-gated channels for both Na⁺ and K⁺ open in only one direction.