Why Are Action Potentials Conducted Usually in One Direction Along

Multiple Choice

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

A) The nodes of Ranvier conduct potentials only in one direction.
B) The brief refractory period prevents reopening of voltage-gated sodium channels.
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.