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: Medicine
[{'content': 'Which of the following causes vasodilation in the pulmonary circulation? \nSelect and explain. \nA. Hypercarbia, B. Hypoxia, C. PGE, D. PGI', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Substances producing pulmonary vasodilation include nitric oxide, prostacyclins, a2 and b2 adrenergic stimulation, histamine etc. Hypercapnia, hypoxy endothelin I, a1 adrenergic, angiotensin II, thromboxane produce pulmonary vasoconstriction.', 'role': 'assistant'}]