This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuroanatomy, Subject name: Anatomy
Sub-arachnoid space ends at 
Select and explain. 
A. S2 level, B. L5 level, C. S1 level, D. L3 level
A: S2 level
Answer: A: S2 level 
Explanation: (A) S2 level> Subarachnoid space surrounds the brain & spinal cord, and ends below at the lower border of the second sacral vertebra.