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': 'For most molar anchor teeth, retainer used is: \nSelect and explain. \nA. W56, B. W7, C. W8, D. W4', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]