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: Anaesthesia
[{'content': 'Longest acting L.A \nSelect and explain. \nA. Bupivacaine, B. Tetracaine, C. Xylocaine, D. Procaine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Tetracaine', 'role': 'assistant'}]