This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
[{'content': 'Most common site for berry aneurysm rupture? \nSelect and explain. \nA. Anterior circulation of brain, B. Posterior circulation of brain, C. Ascending aoa, D. Desending aoa', 'role': 'user'}, {'content': "Answer: B \nExplanation: Harrison's principles of internal medicine 17th edition. * Approximately 85% aneurysms occur in anterior circulation mostly on circle of Willis. Those >7 mm in diameter and those at the top of basilar aery and at the origin of posterior communicating aery are at greater risk of rupture", 'role': 'assistant'}]