设有关系R＝(A，B，C)。与SQL语句SELECT DISTINCT A FROM R WHERE B＝17等价的关系代数表达式是( )。
A. ЛA(
B. ЛB=17(
C. ЛA(σB=17()
D. σB=17(ЛA()
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The best title for this passage may be
A Construction Company under Fire.
B. Fears Haunted in the World.
C. A Debate on Building Upwards.
D. Skyscrapers on the Boom.
It can be inferred from Paragraph 5 that in Japan skyscrapers
A. are already under construction.
B. prove to be quake-resistant.
C. are absolutely prohibited.
D. turn out be energy-efficient.
高应变检测单桩轴向抗压承载力时，采用自由落锤为激振设备，宜重锤低击，锤的最大落距不宜大于( )m。
A. 0.5
B. 1
C. 2
D. 3
物流企业与被投资者的财务关系是( )
A. 权利主体与客体的关系
B. 利益分配的从属关系
C. 投资与受资的关系
D. 所有权与经营权关系
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