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': 'Which of the following drug increases the duration of orthodontic treatment? \nSelect and explain. \nA. Phenytoin, B. Aspirin, C. Paracetamol, D. Vitamin D', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]