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

$A$ : Transmission of the nerve impulse across a synapse is accomplished by neurotransmitters.
$R$ : Transmission across a synapse usually requires neurotransmitters because there is a small space,$i.e.$,synaptic cleft,that separates one neuron from another.

Suppose the terminal ends of an axon are in contact with the dendrites of four adjacent neurons,the nerve impulse of the axon will

The space between two adjoining neurons where the chemical transmitter is released is known as:

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 synaptic knob contains $..........$.