Neurotransmitters, also known as chemical messengers, are endogenous chemicals that enable neurotransmission. Neurotransmitter acts in only one of two ways: excitatory or inhibitory. Gamma-Aminobutyric acid (GABA) is the chief inhibitory neurotransmitter in the central nervous system. GABA is a chemical messenger that is widely distributed in the brain. GABA's natural function is to reduce the activity of the neurons to which it binds and also serves to control the fear or anxiety experienced when neurons are overexcited. So, the correct answer is option B.