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': 'Concentration of lignocaine used – a) 2%b) 4%c) 5%d) 10%e) 1% \nSelect and explain. \nA. bcde, B. abcd, C. abce, D. abde', 'role': 'user'}, {'content': "Answer: C \nExplanation: Lignocaine is used in different concentrations for different regional blocks :- Surface (topical) anesthesia: 4%, Nerve block : 1-2%, Spinal anesthesia : 5%, Epidural : 1-2%, Bier's block : 0.5% and infiltration block : 1-2%.", 'role': 'assistant'}]