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': 'Advantages of rubber dam are \nSelect and explain. \nA. a dry,clean operating field,, B. improved access and visibility,, C. potentially improved properties of dental materials,, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A dry, clean operating field,\nImproved access and visibility,\nPotentially improved properties of dental materials,\nProtection of the patient and operator, and\nOperating efficiency.', 'role': 'assistant'}]