This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
Endothelium derived relaxation factor is supposed to be: (Repeat) 
Select and explain. 
A. Nitric oxide, B. Angiotensin, C. Serotonin, D. Norepinephrine
A: Nitric oxide
Answer: A: Nitric oxide 
Explanation: Ans: A (Nitric oxide) Ref: Pal GK. Synaptic transmission in CNS: ami Neurotransmitters. In: Textbook of medical physiology. 2nd ed. Ahuja publishing house. 2011; 100: 794.Explanation:Nitric oxide is also called as EDRF (Endothelial derived relaxation factor)Formed from arginine by NO synthase which needs NADPHIt mediates the action of many other vasodilators - Histamine, Ach, hradykinin. VIP, substance P