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【单选题】
设有关系模式R(U,F)，其中U＝{X，Y，Z}，F＝{X→Y}，则R的码是A.
X
B.
Y
C.
XY
D.
XZ
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皮皮学刷刷变学霸
举一反三
【单选题】—You never stay up till midnight, do you? —___________. But I think it’s bad for our health.
A.
No, never
B.
No, sometimes
C.
Yes, never
D.
Yes, sometimes
【单选题】—Time is limited. I have to finish this tonight. —But it’s midnight now and you should have a sleep ______ much work you have to do.
A.
however
B.
no matter
C.
although
D.
whatever
【单选题】-----Will you attend tomorrow’s meeting? -----No, _____ I am invited, I will not go there.
A.
even though
B.
if
C.
unless
D.
because
【简答题】blended learning给教学系统设计的启示。
【单选题】— Excuse me, is this shop open all day? — ____. It's only open from 9 a.m.to midnight. [ ]
A.
Well, I'm not sure
B.
Oh, it's nothing special
C.
Sorry, I'm afraid not
D.
Yes, of course not
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