When Synaptic Vesicles Collapse into the Plasma Membrane, and Then

When synaptic vesicles collapse into the plasma membrane, and then participate in endocytosis, they

A) pull back into their lumen the soluble contents of the extracellular saline.
B) pull back selectively transmitter from the synaptic cleft.
C) do not pull anything back into the vesicle; they are empty.
D) pull back selectively the breakdown products of transmitter.
E) pull back acetylcholinesterase from the synaptic cleft.