This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Circulation, Subject name: Physiology
[{'content': 'The vasodilatation produced by carbon dioxide is maximum in: \nSelect and explain. \nA. Kidney, B. Brain, C. Liver, D. Hea', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Inhalation of 7% CO2 increases cerebral blood twofold. Cerebral blood vessels are very sensitive to CO2 tension. Hepatic aerial system is sensitive to adenosine; it brings about vasodilatation. Adenosine is the most impoant vasodilator of coronary vessels. CO2, H+, K+, hypoxia also cause reactive hyperemia. NO, an endothelium-derived relaxing factor is an impoant vasodilator of renal aerioles.', 'role': 'assistant'}]