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 longest acting, most potent and most toxic LA is: \nSelect and explain. \nA. Lidocaine, B. Dibucaine, C. Bupivacaine, D. Tetracaine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]