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【单选题】
设有关系模式 R ( X , Y , Z , W ) 与它的函数依赖集 F ={ XY → Z , W → X } , 则 R 的主码为( )。A.
XY
B.
XW
C.
YZ
D.
YW
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【单选题】---Volunteering is becoming popular in China . --- Yeah, people are now aware that helping others is helping themselves.
A.
naturally
B.
successfully
C.
thoroughly
D.
increasingly
【单选题】My name is Mary Brown, You can call me _________． [ ]
A.
Mary
B.
Miss Mary
C.
Mr. Smith
【单选题】—This boy is my friend. _______ name is Tom. —_____ name is Mary. Nice to meet you.
A.
His, Her
B.
My, My
C.
My, His
D.
His, My
【单选题】With its rising economy in China, ______ car is becoming ______ common means of transportation. [ ]
A.
a; the
B.
/; a
C.
the; a
D.
the; the
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