This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
What is true statement of the following? 
Select and explain. 
A. Synaptic transmission is unidirectional, B. Glutamate is the major excitatory neurotransmitter in the nervous system, C. GABA and glycine are the major inhibitory neurotransmitters, D. All of above
D: All of above
Answer: D: All of above 
Explanation: synaptic transmission is always a unidirectional flow.Glutamate is considered as an excitaroty neurotrasmitter and GABA and glycine inhibitory. Ref: KD Tripathi 8th ed, central nervous system.