题目内容

下列关系模型中,能使用经运算后得到的新关系中的属性个数多于原来关系中的属性个数的是( )。

A. 选择
B. 联接
C. 投影
D. 并

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______ is a map of China over there on that wall.

A. This
B. That
C. Those

Here is the ______ list for the class with all your names on it.

A. contact
B. contract
C. connect

______ are the names of all the students.

A. This
B. These
C. That

-______ to meet you.-______ to meet you too.

A. Nice, glad
B. Glad, Please
C. Nice, pleased
D. Nice, Pleased

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