折射率指光在真空中的传播速度与光在该介质中的传播速度之比。()
按照珠宝质量从优至劣可分为透明、亚透明、半透明、微透明、不透明。越是晶莹剔透的宝石越是珍贵。()
What would me man like to do after meal?
A. He"d like to stay with his family.
B. He"d like to help his wife do the dishes.
C. He"d like to go bowling.
D. He"d like to deal with the leftovers.
I型钻石又依据N原子存在的不同形式划分为Ia型、Ib型。()