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: Biochemistry
[{'content': 'In the physiologic system, nitric oxide is known to act through \nSelect and explain. \nA. Cyclic AMP, B. Calcium ions, C. Cyclic GMP, D. Prostacyclins', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]