.When a nerve impulse reaches the transmissive segment of a neuron,A. Calcium is pumped into the neuron and neurotransmitter diffuses out through channels.B. calcium is released from the neuron along with neurotransmitter from synaptic vesicles.C. calcium diffuses into the neuron and neurotransmitter is released by exocytosis.D. calcium and neurotransmitter diffuse into the synaptic knob.E calcium is immediately pumped out of the neuron and vesicles of neurotransmitter undergo phagocytosis.