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
[{'content': 'Which of the following is not a second messenger \nSelect and explain. \nA. c-AMP, B. IP3, C. Guanylyl cyclase, D. Diacylglycerol (DAG', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. c. Guanylyl cyclase', 'role': 'assistant'}]