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': 'In peripheral nerve block, which of the following\nlocal anesthetics has the longest duration of\naction?\t(OR)\nWhich of the following local anesthetic agent would be preferred in prolonged surgical procedures? \nSelect and explain. \nA. Bupivacaine, B. Cocaine, C. Lignocaine, D. Prilocaine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]