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: Pharmacology
All are true about nitric oxide, EXCEPT: 
Select and explain. 
A. Regulates vasomotor tone, B. Acts via cAMP, C. Present in cigarette smoke, D. It is important in penile erection
B: Acts via cAMP
Answer: B: Acts via cAMP 
Explanation: Nitric oxide is a potent vasodilator and serves to regulate vascular tone. Produced in the endothelium it freely diffuses to the nearby smooth muscle cell and activates a soluble guanylyl cyclase (sGC) raising cytosolic cGMP concentration. This in turn activates a cGMP-dependent protein kinase (PKG).