What does a transporter protein do at a synapse?

a. It carries neurotransmitter molecules from the presynaptic neuron to the postsynaptic neuron.

b. It carries neurotransmitter molecules from the cell body to the presynaptic terminal.

c. It carries neurotransmitter molecules from neurons that have too much into neurons that need more.

d. It pumps used neurotransmitter molecules back into the presynaptic neuron.