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': 'Application of 2-3 layers of varnish covers: \nSelect and explain. \nA. 55% of surface area, B. 60-80% of surface area, C. 90% of surface area, D. 70% of surface area', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Single layer of varnish covers 55% of surface area.', 'role': 'assistant'}]