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[单选题]
设有C语句序列:intarr[5][5],*p1p1=&arr[3][3],那么能够输入数组3行3列元素值的是()。
A.scanf("%d",p1[3])
B.scanf("%d",arr[3])
C.scanf("%d",p1)
D.scanf("%d",p1+3)
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A.scanf("%d",p1[3])
B.scanf("%d",arr[3])
C.scanf("%d",p1)
D.scanf("%d",p1+3)
设有关系R=(A,B,C),和关系代数表达式:
Ⅰ.πA,C(σB=5(R))
Ⅱ.σB=5(πA,C(R))
Ⅲ.σπA,C(πB=5(R))
上述关系代数表达式中,与SQL语句selectdistinct A,C from R where B=5等价的是
A.都等价
B.Ⅲ
C.Ⅱ
D.Ⅰ