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': 'ECG changes can first be observed when level of lignocaine is more than \nSelect and explain. \nA. 5 — 6 ug/ml, B. 10 — 12 ug/ml, C. 2 — 4 ug/ml, D. 1.2 ug/ml', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]