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': 'How much lignocaine is present in 2.0ml of 2% lignocaine solution? \nSelect and explain. \nA. 40 mg, B. 20 mg, C. 30 mg, D. 2 mg', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]