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【简答题】
有两个关系S(A, B, C, D)和T(C, D, E, F),分别包括N1,N2两个,N2 > N1 > 0,对下列每个关系代数表达式,计算在使表达式有意义的情况下,可以得到的最大、最小的数目及列数。 1 S∪T 2 S∩T 3 S-T 4 S×T 5 σA=10(S) 6 ∏A,B(S) 7 S T 8ΠC,D(S)×T
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皮皮学刷刷变学霸
举一反三
【单选题】Mr. Stone sat tight-lipped, until toward the end when he slowly turned to the right and then to the left, looking at each of us in turn as if he wanted to _________ the picture on his mind.
A.
remember
B.
record
C.
take
D.
register
【单选题】Mr.Wood guarantees that Mr. Feng will ()their equipment.
A.
satisfy
B.
satisfactory
C.
be satisfied with
D.
satisfy with
【简答题】颜色模式中色光三原色是指 、色料(印刷)三原色是指 。
【单选题】The jeweler assured Mr. White that the stone was a ___ diamond and not an imitation.
A.
graceful
B.
glittering
C.
genuine
D.
genius
【简答题】颜色三原色是指( )、( )、( )三色
【单选题】The beautiful stone _________ as much as 2.5 tons was placed in Mr. White’s garden last week.
A.
weighed
B.
weighing
C.
to be weighed
D.
being weighed
【简答题】Mr. Stone sat ______________(紧闭嘴巴的), until toward the end when he slowly turned to the right and then to the left, looking at each of us in turn as if he wanted to ______________(深深记住)the picture on h...
【单选题】Why won't Mr. Stone come to the clinic tomorrow?
A.
He can't spare the time.
B.
The clinic will be closed.
C.
Dr.Milton won't come to work.
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