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': 'A series may have all except: \nSelect and explain. \nA. No mode, B. One mode, C. Many mode, D. Negative mode', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]