Answer:
B) signals the exocytosis of the neurotransmitter.
Step-by-step explanation:
The arrival of action potential at the presynatic neuronal membrane caused the influx of Ca+ into the presynaptic neuron, This leads to the migration and fission of acetycholine neurotransmitter contained vesicles to the tips of the presynaptc neurons, and eventual emptying into the synaptic cleft by exocytosis.
Thus it is the influx of Ca+ which stimulated the migration and emptying of the acetycholine neurotransmitters by exocytosis.
The acetycholine binded with the receptors on the post-synaptic neuron for action potential to generate in the post synaptic neuron as IPSP or EPSP