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. – a) Bupivacaineb) Tetracainec) Xylocained) Procaine \nSelect and explain. \nA. ac, B. a, C. ad, D. ab', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Dibucaine is the longest acting LA (duration is 2.5-3.5 hours).\nAmongst the given options tetracaine & bupivacaine are longest acting (both have duration of 2-3 hours).\nDecreasing order of duration :- Dibucaine (longest acting) > Bupivacaine = Tetracaine = Ropivacaine = Etidocaine > Prilocaine = Lignocaine = Mepivacaine = Cocaine > Procaine > chlorprocaine.', 'role': 'assistant'}]