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【单选题】
实体关系模型中,要从给定的关系中找出若干属性组成新的关系,应该使用的关系运算是( )。A.
投影
B.
选择
C.
联接
D.
自然联接
拍照语音搜题，微信中搜索"皮皮学"使用
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举一反三
【单选题】There is a crowd of people in front of the house over there. What do you suppose _____ there?
A.
is happened
B.
has happened
C.
happening
D.
to have happened
【简答题】Is there a mistake on the bill? What is it? Yes, there is. They didn't order any coconut juice. But there is a charge for coconut juice.
【简答题】The principal difference between lossless and lossy compression is the __________ or __________ of the quantizer.
【判断题】Interframe compression is lossy while intraframe compression is lossyless
A.
正确
B.
错误
【单选题】—Whose watch is lost? —Mr. Smith's. Look! He _____ it here and there. [ ]
A.
looked
B.
was looking for
C.
looks for
D.
is looking for
【简答题】D3 Where is the woman now? What is she doing there? What is she working for?
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