This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
All are true about nitric oxide except 
Select and explain. 
A. Acts through cAMP, B. Helps to regulate vascular tone, C. Impoant role in penile erection, D. Present in low concentration in cigarette smokers
A: Acts through cAMP
Answer: A: Acts through cAMP 
Explanation: NO acts through guanylyl cyclase.Ref: Ganong&;sReview of medical physiology, 24th edition.Pg no. 151