Final answer:
The most common inhibitory neurotransmitters in the CNS are GABA and glycine, which both play critical roles in reducing neural activity by causing hyperpolarization of the postsynaptic cell. Glutamate, however, is an excitatory neurotransmitter. Therefore, the correct answer is D. GABA and glycine.
Step-by-step explanation:
The most common inhibitory neurotransmitters of the central nervous system (CNS) are GABA (gamma-aminobutyric acid) and glycine. GABA is the main inhibitory neurotransmitter in the CNS, crucial for reducing neuronal excitability throughout the nervous system. On the other hand, glycine acts primarily in the spinal cord and brainstem to serve a similar function. Both neurotransmitters cause hyperpolarization of the postsynaptic cell when their specific receptors are activated, thereby inhibiting neural activity. Glutamate, by contrast, is an excitatory neurotransmitter, promoting depolarization of the postsynaptic cell, and is not an inhibitory neurotransmitter.
The correct answer to the question 'Which is/are the most common inhibitory neurotransmitter(s) of the CNS?' would be D. GABA and glycine, as they are both widely recognized for their role in diminishing neural activity and promoting inhibition in the CNS.