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': 'When composites are given, exposed dentin should be covered with \nSelect and explain. \nA. Varnish, B. Calcium hydroxide, C. Phosphoric acid, D. ZnO eugenol cements', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]