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 retainerless matrix system with four types of bands fitted around any teeth regardless of its circumference is called \nSelect and explain. \nA. Tofflemire matrix, B. Auto matrix, C. Ivory No. 1 matrix, D. Ivory No. 8 matrix', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]