This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Local and Regional Anesthesia), Subject name: Anaesthesia
[{'content': 'Local anesthetics block which ion channel: \nSelect and explain. \nA. K+, B. Ca+, C. Na+, D. Cl', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans (c) Na+Ref: KDT 6th ed. / 353', 'role': 'assistant'}]