在设计数据库的时候要使用标准化原则,标准化有助于消除数据库中的数据冗余。标准化有多种

题型:单项选择题

问题:

在设计数据库的时候要使用标准化原则,标准化有助于消除数据库中的数据冗余。标准化有多种形式,其中______通常被认为在性能、扩展性和数据完整性方面达到了最好平衡。

A.1NF
B.2NF
C.3NF
D.4NF

考点:计算机软件水平考试初级信息处理技术员信息处理技术员
题型:单项选择题

阅读理解。

     The famous scientist and thinker, Charles Darwin, was born on February 12, 1809. As a boy,

Charles liked to go for walks in the fields and forests, watching nature, and comparing what he saw

with everything he had read in science books. He also liked collecting very much. He collected many

things: birds, stones, and leaves.

     At sixteen Darwin was sent to Edinburgh University to become a doctor. But he was interested

in the history of nature.

     Then he was sent to study at Cambridge University. There he studied until 1831.

     Some time later he heard that the ship Beagle was going on a trip to South America and wanted a

scientist. His professor advised him to go. So when the Beagle left England in December 1831, Darwin

was on it.

     The expedition lasted almost five' years. Darwin saw many new plants and animals. He collected

all kinds of plants.

     In 1842 Darwin went to live in Kent, and there he continued his studies of change in nature. Darwin

understood that plants and animals are not always the same, and that they really change. By 1859

Darwin had finished his famous book The, Origin of Species. It made a great noise in the world of

science. In 1871 Darwin wrote another important book.

     Darwin continued his studies in science until he died in 1882.

1. Charles Darwin was a great _____ scientist.

A. German        

B. French

C. English          

D. American

2. As a boy, Darwin liked reading _____ books.

A. science          

B. chemistry

C. history          

D. medical

3. Darwin studied at Cambridge University _____ 1831. 

A. after          

B. since

C. before          

D. in

4. On the ship Beagle Darwin worked as a _____. 

A. teacher        

B. doctor

C. professor        

D. scientist

5. In 1871 Darwin wrote another important book _____. 

A. The Origin of Species

B. The Theory of Relativiy

C. The Theory of Evolution(《迸化论》)

D. On Practice

题型:单项选择题

碳酸氢钠与盐酸中和时所产生的二氧化碳可导致

A.胃胀和嗳气

B.心动过速

C.腹泻

D.转氨酶升高

E.胃内压力降低

题型:单项选择题

男性,71岁。患慢性支气管炎和阻塞性肺气肿近10年,曾因呼吸衰竭抢救2次。目前动则气急,不吸氧时动脉血气分析PaO26.7kPa(50mmHg),PaCO26.7kPa(50mmHg)。正在医生指导下接受呼吸康复治疗。

为锻炼呼吸肌力和耐力,此例患者可以选择()

A.吸气阻力锻炼

B.双水平气道正压呼吸支持

C.间歇正压呼吸支持

D.呼气末正压呼吸支持

E.体外负压呼吸支持

题型:单项选择题

一个正三棱锥的四个面上分别标有数字1,2,3,4.连续抛掷两次,以底面上数字作为掷出的数字,记X,Y分别表示两次掷出数字的最大值与最小值.计算X+Y与X-Y的协方差矩阵

的逆矩阵.

题型:单项选择题

相对安全和绝对安全的看法有何不同?对安全管理行为有何影响?

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