萃取操作时选择性系数的大小反映了萃取剂对原溶液分离能力的大小，选择性系数必须大于1，并且越大越有利于分离。
A. 对
B. 错
分配系数片KA＜1表示萃余相中A组分的浓度＜萃取相中A组分的浓度。
A. 对
B. 错
Do you know when we will have the new year party?
A. No problem
B. Yes, it is.
C. In the classroom
D. Tomorrow evening
How will you celebrate your first summer holiday in China?
A. It is in spring
B. We often throw a party
C. That's a good idea.
D. I'll go traveling
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