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: Medicine
Pain insensitive structure - 
Select and explain. 
A. Middle cerebral artery, B. Choroid plexus, C. Dural sheath, D. Falx cerebri
B: Choroid plexus
Answer: B: Choroid plexus 
Explanation: None