This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Nitric Oxide is produced in: 
Select and explain. 
A. Endothelium, B. Plasma, C. Platelets, D. Serum
A: Endothelium
Answer: A: Endothelium 
Explanation: A i.e. Endothelium Nitric oxide is synthesized from arginine by the enzyme NO synthetase (NOS) in endothelial cellsQ. It causes vasodilation.