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
[{'content': 'The main barrier for diffusion of LA is: \nSelect and explain. \nA. Epineurium, B. Endoneurium, C. Perineurium, D. All of the above.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The main barrier for diffusion of LA is the perineurium. Endoneurium / Nerve membrane is the acute site of action and depend on lipid solubility of drug.', 'role': 'assistant'}]