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【单选题】
关系和关系模式之间的关系是()A.
关系是型，关系模式是它的值
B.
关系模式是型，关系是它的值
C.
关系模式是关系的集合
D.
关系是关系模式的集合
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皮皮学刷刷变学霸
举一反三
【单选题】The project ______ completed by now but as there has been a lack of electricity it is still only half finished.
A.
was to have been
B.
is to be
C.
is
D.
was
【单选题】We are of course() that the period for completion of your project has already been exceeded .
A.
know
B.
to know
C.
aware
D.
sure
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