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: Pharmacology
[{'content': 'Which of the following is the longest acting LA? \nSelect and explain. \nA. Mepivacaine, B. Bupivacaine, C. Dibucaine, D. Chlorprocaine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Dibucaine: Longest acting LA.\nChlorprocaine: Shortest acting LA.', 'role': 'assistant'}]