This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc., Subject name: Physiology
All of the following act as gaseous neurotransmitters except 
Select and explain. 
A. Oxygen, B. Carbon monoxide, C. Nitric oxide, D. H2S
A: Oxygen
Answer: A: Oxygen 
Explanation: (A) Oxygen # TYPES OF NEUROTRANSMITTERS:> There are many different ways to classify neurotransmitters. Dividing them into amino acids, peptides, and monoamines is sufficient for some classification purposes.> Major neurotransmitters:> Amino acids: glutamate, aspartate, D-serine, Gamma-aminobutyric acid (GABA), glycine> Monoamines and other biogenic amines: dopamine (DA), norepinephrine (noradrenaline; NE, NA), epinephrine (adrenaline), histamine, serotonin (SE, 5-HT)> Peptides: somatostatin, substance P, opioid peptides> Others: acetylcholine (ACh), adenosine, anandamide, nitric oxide, etc..