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': 'Local anesthetics act by : \nSelect and explain. \nA. Affecting at the spinal level, B. Affecting the Na+ channels, C. Affecting the K+channels, D. Blocking axonal transport', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]