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 using the acid etch technique to restore a Class IV\nfracture, exposed dentin should first be covered with: \nSelect and explain. \nA. Cavity varnish, B. Phosphoric acid, C. A calcium hydroxide liner, D. Zinc oxide-eugenol cement', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]