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
The anesthetic drug injected for paravertebral block is least likely to diffuse to 
Select and explain. 
A. Epidural space, B. Subarachnoid space, C. Intercostal space, D. Superior and inferior paravertebral space
B: Subarachnoid space
Answer: B: Subarachnoid space 
Explanation: None