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': 'Kesling positioner is a \nSelect and explain. \nA. Retainer, B. Fixed device, C. Removable appliance, D. Functional appliance', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]