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
Which of the following is not a second messenger 
Select and explain. 
A. c-AMP, B. IP3, C. Guanylyl cyclase, D. Diacylglycerol (DAG
C: Guanylyl cyclase
Answer: C: Guanylyl cyclase 
Explanation: Ans. c. Guanylyl cyclase