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
Longest acting L.A. – a) Bupivacaineb) Tetracainec) Xylocained) Procaine 
Select and explain. 
A. ac, B. a, C. ad, D. ab
D: ab
Answer: D: ab 
Explanation: Dibucaine is the longest acting LA (duration is 2.5-3.5 hours).
Amongst the given options tetracaine & bupivacaine are longest acting (both have duration of 2-3 hours).
Decreasing order of duration :- Dibucaine (longest acting) > Bupivacaine = Tetracaine = Ropivacaine = Etidocaine > Prilocaine = Lignocaine = Mepivacaine = Cocaine > Procaine > chlorprocaine.