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': 'The pH of APF gel is - \nSelect and explain. \nA. 2.3, B. 3.2, C. 2.32, D. 1.23', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]