Which of the following does not act as a neurotransmitter?

Which chemical substance is responsible for the transmission of nerve impulses across the synapse from one neuron to another?

Identify the location and function of the following structures:
$(1)$ Synaptic Knob
$(2)$ Bipolar nerve cell

Select the incorrect statement regarding synapses :

Which of the following is released by the parasympathetic nervous system?

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