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': 'The ideal dimension for the luting agent space is \nSelect and explain. \nA. 0-20 microns, B. 20-40 microns, C. 40-80 microns, D. 80-120 microns', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]