The chemical causing the transmission of nerve impulse across synapses is

Which of the following does not act as a neurotransmitter?

Five events in the transmission of a nerve impulse across a synapse are given below:
$a.$ Certain ion channels open,allowing ions to enter and generate a new action potential in the post-synaptic neuron.
$b.$ Neurotransmitter molecules bind to receptors on the post-synaptic membrane.
$c.$ Synaptic vesicles fuse with the pre-synaptic membrane,and the neurotransmitter is released into the synaptic cleft. Depolarization of the pre-synaptic membrane is induced.
$d.$ An action potential reaches the axon terminal.
What is the correct sequence of these events?

The gap between the axon of one neuron and the dendrite of another is called . . . . . . .

What is the junction between the axon of one neuron and the dendrite of another neuron called?

The pre-synaptic part is: