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: Surgery
[{'content': 'Pain insensitive structure in brain is : \nSelect and explain. \nA. Flex cerebri, B. Dural sheath surrounding vascular sinuses, C. Middle meningeal aery, D. Choroid plexus', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Choroid plexus Choroid plexus is pain insensitive structure. Harrison writes:-"relatively few cranial structures are pain- producing; these include the slap\' middle meaningeal aery, dural sinuses, falx cereberi, and proximal segments of the large pail aeries. The ventricular ependyma, choroid plexus, pail veins, and much of the brain parenchyma are not pain-producing."', 'role': 'assistant'}]