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': 'Lithium disilicate containing crystals in ceramic crown are? \nSelect and explain. \nA. IPS Empress, B. Captek, C. Dicor, D. IPS Empress 2', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]