下列题的关系代数操作是基于如下的关系R和S: R A B C a1 b1 5

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问题:

下列题的关系代数操作是基于如下的关系R和S:

R
A B C
a1 b1 5
a1 b2 6
a2 b3 8
a2 b4 12
S
B E
b1 3
b2 7
b3 10
b4 2
b5 2

若结果如下,这是对关系R和S执行了( )。

A R.B C E
a1 b1 5 3
a1 b2 6 7
a2 b3 8 10
a2 b4 12 2

考点:计算机等级考试数据库技术三级数据库技术笔试
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关于电解NaCl水溶液,下列叙述正确的是[ ]

A.电解时在阳极得到氯气,在阴极得到金属钠

B.若在阳极附近的溶液中滴入KI溶液,溶液呈棕色

C.若在阴极附近的溶液中滴入酚酞试液,溶液呈无色

D.电解一段时间后,将全部电解液转移到烧杯中,充分搅拌后溶液呈中性

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房地产经纪行业管理的基本作用是( )。

A.维护社会整体利益

B.维护委托人的经济利益

C.维护房地产经纪行业的正常发展

D.维护房地产经纪机构的经营信誉

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Perhaps the most extraordinary (奇特的) building put up in the nineteenth century was the Crystal Palace (水晶宫) which was built in Hyde Park for the Great Exhibition of 1851. The Crystal Palace was different from all the other buildings in the world, for it was made of iron and glass. It was one of the biggest buildings of all the time and a lot of people from many countries came to see it. Plenty of goods were sent to the exhibition from all parts of the world. There was also a great deal of machinery on show. Though in those days, traveling was not as easy as it is today, steamboats carried thousands of visitors across the Channel from Europe. On arriving in England, they were taken to the Crystal Palace by train. There were six million visitors in all, and the money from the exhibition was used to build museums and colleges. Later the Crystal Palace was moved to the South London. It remained one of the most famous buildings in the world until it was burnt down in 1936.

小题1:The Crystal Palace was built up              .

A.in the 1950s

B.in the 1900s

C.shortly before 1851

D.before 1951小题2:People from many countries came to the Crystal Palace mainly to            .

A.buy goods

B.visit an exhibition

C.travel around

D.enjoy the Crystal Palace itself小题3:What happened to the Crystal Palace in 1936?

A.It caught a terrible fire.

B.It disappeared suddenly.

C.It went to the South of London.

D.It was rebuilt.小题4:The Crystal Palace was famous to all because            .

A.it is the biggest building in the world

B.so many visitors had been there

C.it was made of iron and glass

D.it was burnt down at last小题5:The writer              .

A.thought the Crystal Palace very useful

B.sang high praise for the Crystal Palace

C.wanted the Crystal Palace to be rebuilt

D.was one of the visitors to the Crystal Palace

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建设有中国特色的行政学的充分的理论依据是()

A.邓 * * 理论

B.马克思主义

C.社会公正

D.行政管理二重性

题型:单项选择题

环境的不可逆变化,如水土流失、土地沙漠化等主要是由()引起的。

A.自然干扰

B.人为干扰

C.自然促进

D.人为促进

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