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': 'Cerebrospinal fluid is filled between: \nSelect and explain. \nA. Dura mater and arachnoid mater, B. Arachnoid mater and Pia mater, C. Pia mater and Brain surface, D. Dura mater and Pia mater', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Subarachnoid space is a wide space between the pia and the arachnoid, filled with cerebrospinal fluid (CSF).\nIt surrounds the brain and spinal cord like a water cushion. The spinal subarachnoid space is wider than the space around the brain. It is widest below the lower end of the spinal cord where it encloses the cauda equina. Lumbar puncture is usually done in the lower widest part of the space, between third and fourth lumbar vertebrae.\nReference: B D Chaurasia’s Head and Neck anatomy, 6th ed page no 184', 'role': 'assistant'}]