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: Pharmacology
[{'content': 'Atherosclerosis impedes coronary blood flow by which of the following mechanisms? \nSelect and explain. \nA. Plaques obstruct the vein, B. Plaques obstruct the artery, C. Blood clots form outside the vessel wall, D. Hardened vessels dilate to allow blood to flow through', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Option A: Arteries, not veins, supply the\xa0coronary\xa0arteries with oxygen and other nutrients.\nOption C: Atherosclerosis is a direct result of plaque formation in the artery.\nOption D: Hardened vessels can’t dilate properly and, therefore, constrict blood flow.', 'role': 'assistant'}]