只要是有色透明的非均质体宝石都可以通过二色镜肉眼观察到二色性
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当一轴晶的有色宝石的o光和e光具有不同的颜色时为二色性
A. 对
B. 错
要用二色镜观察宝石的多色性,待测样品一定要有色、透明、具有双折射率的宝石
A. 对
B. 错
We _______ the airport at 5 o'clock.
A. arrive
B. leave from
C. depart from
D. get
Stockton and his son put all the stuff up ________ this doorin case the people outside break into the shelter.
A. against
B. back
C. forward