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: Dental
[{'content': 'Avulsed tooth dip into the citric acid because \nSelect and explain. \nA. To remove periodontal ligament, B. To increase the surface area, C. To provide a barrier, D. To increase tension', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]