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
True about nitric oxide: 
Select and explain. 
A. Free radical, B. Vasodilator, C. Oxidizing agent, D. All
D: All
Answer: D: All 
Explanation: A i.e. Free radical; B i.e. Vasodilator; C i.e. Oxidizing agent