Which statement correctly describes the cellular mechanism of uptake (sometimes called "reuptake") of neurotransmitter from a synapse into the axon terminal?

a. Neurotransmitter uptake is by an ATP-dependent active transport pump
b. Neurotransmitter uptake is by a secondary active transport protein that depends on the sodium gradient across the membrane
c. Neurotransmitter uptake is by receptor-mediated endocytosis
d. Neurotransmitter uptake is by facilitated diffusion from a region of high concentration to a region of low concentration