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': 'Pain insensitive structure \nSelect and explain. \nA. Middle cerebral aery, B. Choroid plexus, C. Dural sheath, D. Falx cerebri', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The cranium, brain parenchyma, ependymal lining of the ventricles, and choroid plexus are all pain insensitive Ref Harrison20th edition pg 2345', 'role': 'assistant'}]