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: Anatomy
[{'content': 'Which of the following is not considered a part of Circle of Willis? \nSelect and explain. \nA. Anterior cerebral artery, B. Middle cerebral artery, C. Posterior communicating artery, D. Posterior cerebral artery', 'role': 'user'}, {'content': "Answer: B \nExplanation: Circle of Willi's is formed by:-\n\nIn front: anterior communicating artery.\nAnterolaterally: two anterior cerebral artery.\nLaterally: proximal segments of both internal carotid arteries.\nPostero-laterally: two posterior communicating arteries.\nBehind: proximal segments of both posterior cerebral arteries, arising at bifurcating terminal of the basilar artery.", 'role': 'assistant'}]