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
Lithium disilicate containing crystals in ceramic crown are? 
Select and explain. 
A. IPS Empress, B. Captek, C. Dicor, D. IPS Empress 2
D: IPS Empress 2
Answer: D: IPS Empress 2 
Explanation: None