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': 'Pain insensitive structure in brain is - \nSelect and explain. \nA. Falx cerebri, B. Dural sheath surrounding vascular sinuses, C. Middle meningeal artery, D. Choroid plexus', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]