This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Brain , Subject name: Anatomy
[{'content': 'Which aery is formed by joining of 2 veebral aeries? \nSelect and explain. \nA. Basal aery, B. Middle cerebralaery, C. Posterior cerebral aery, D. Basilar aery', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Basilar aery is formed by the union of two veebral aeries at the lower border of pons. Middle cerebral aery is a branch of internal carotid aery. Posterior cerebral aery is a branch of basilar aery. (Ref: Vishram Singh textbook of clinical neuroanatomy, second edition pg-174,176)', 'role': 'assistant'}]