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 greatest potential for wearing exists when : \nSelect and explain. \nA. Porcelain opposes porcelain., B. Porcelain opposes acrylic., C. Porcelain opposes gold., D. Porcelain opposes natural teeth.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]