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 is a removable space regainer \nSelect and explain. \nA. Open coil, B. Gerber, C. Hotz, D. Split saddle', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Split saddle is a removable space regainer while other three are fixed space regainer.', 'role': 'assistant'}]