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 are unpaired vessel in CNS : \nSelect and explain. \nA. Anterior-cerebral aery, B. Basilar aery, C. Posterior-cerebellar aery, D. Posterior-communicating aery', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Basilar aery', 'role': 'assistant'}]