This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
[{'content': 'Pulmonary vasoconstriction is caused by \nSelect and explain. \nA. Prostacyclin, B. Alpha-2 stimulation, C. Hypoxia, D. Histamine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Prostacyclin, alpha 2 stimulation, and Histamine are potent vasodilators.Ref: Ganong review of medical physiology 23rd edition Page no: 563', 'role': 'assistant'}]