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': 'Activity of all local anaesthetic solutions is affected by pH of the tissue or infection except: \nSelect and explain. \nA. Propoxycaine, B. Benzocaine, C. Lidocaine, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: As benzocaine has no charge', 'role': 'assistant'}]