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': 'Twin wire appliance is a \nSelect and explain. \nA. Fixed appliance, B. Removable appliance, C. Functional appliance, D. Sectional fixed appliance', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]