The correct option is D All of the above
Neurotransmitters are the brain chemicals that relay signals between neurons. There are two kinds of neurotransmitters viz., inhibitory and excitatory. Excitatory neurotransmitters stimulate the brain. Those that calm the brain and help create balance are called inhibitory. Examples of excitatory neurotransmitters are dopamine, epinephrine and norepinephrine. Examples of inhibitory neurotransmitters are serotonin and GABA. Thus, the correct answer is option D.