This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Physiology
Inhibitory neurotransmitter of central nervous system is: 
Select and explain. 
A. Aspartate, B. Gamma-aminobutyric acid, C. Glutamate, D. Acetylcholine
B: Gamma-aminobutyric acid
Answer: B: Gamma-aminobutyric acid 
Explanation: Ans. B. Gamma-aminobutyric acidGAMMA-AMINOBUTYRIC ACID is an inhibitory neurotransmitter found in brain and retina which is responsible for presynaptic inhibition.