This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Physiology
NO is synthesized by - 
Select and explain. 
A. Uracil, B. Aspartate, C. Guanosine, D. Arginine
D: Arginine
Answer: D: Arginine 
Explanation: Ans. is 'd' i.e., Arginine * Nitric oxide, also called endothelium-derived-relaxing factor (EDRF), is formed from amino acid arginine, by the action of the enzyme NO synthase, which is cytosolic.ArginineNO synthase-------Citrulline + NO