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': "An example of preadjusted appliance is \nSelect and explain. \nA. Frankel appliance, B. Begg's light wire appliance, C. Angles edge wire appliance, D. Andrew's straight wire appliance", 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]