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【单选题】
超星学习通的产品经理是谁?A.
B.
C.
D.
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举一反三
【单选题】关于关系模式的关键字，以下说法正确的是（）。
A.
一个关系模式可以有多个主关键字
B.
一个关系模式可以有多个侯选关键字
C.
主关键字可以取空值
D.
关系模式必须有主关键字
【单选题】The pills him.If only he had taken them regularly.
A.
could help
B.
may help
C.
must have helped
D.
might have helped
【单选题】The lad couldn’t ______ even if he ______ in time.
A.
have been saved; had been treated
B.
be saved; have been treated
C.
be saved; had been treated
D.
had been saved; would have been treated
【单选题】______for the worst in advance and you wont he disappointed.
A.
Prepare
B.
When preparing
C.
Having prepared
D.
If you prepare
【单选题】关于关系模式的关键字,以下说法正确的是( )。
A.
主关键字可以取空值
B.
一个关系模式可以有多个主关键字
C.
一个关系模式可以有多个侯选关键字
D.
关系模式必须有主关键字
【单选题】—Why didn't Mr. Smith give you one of his newlypublished books? —I didn't want one, but he would have given me one if I ________. [ ]
A.
did
B.
would
C.
will
D.
had
【简答题】根据句意及所给首字母提示，完成句中所缺的单词。 1. If you are ill,you should take some m________ and have a good rest. 2. Millions of t________ from all over the world came to Shanghai during the World Expo. 3. The 2011 New ...
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