— _____________ she get up at 6: 00?

— No, she _____________. [ ]

A. Do, don't

B. Does, doesn't

C. Do, doesn't

关系代数中，从两个关系的笛卡儿积中，选取它们的属性间满足一定条件的元组的操作，称为( )。

A．投影

B．选择

C．自然连接

D．θ连接