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': 'In 3x3 table, the degree of freedom is \nSelect and explain. \nA. 3, B. 6, C. 9, D. 4', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]