This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Mechanism of action of nitric oxide is \nSelect and explain. \nA. Increase cAMP, B. Increase cGMP, C. Increase PGE2, D. Increase PGD4', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Refer kDT 7/e 568 Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula NO. It is one of the principal oxides of nitrogen. Nitric oxide is a free radical, i.e., it has an unpaired electron, which is sometimes denoted by a dot in its chemical formula, i.e., *NO. Nitric oxide is also a heteronuclear diatomic molecule, a historic class that drew researches which spawned early modern theories of chemical bonding.', 'role': 'assistant'}]