问题 单项选择题

设F是属性组U上的一组函数依赖,下列叙述正确的是

A.若Y

X,则X→Y为F所逻辑蕴含

B.若X

U,则X→Y为F所逻辑蕴含

C.若X→Y为F所逻辑蕴含,且Z

U,则X→YZ为F所逻辑蕴含

D.若X→Y及Y→Z为F所逻辑蕴含,则X→Z为F所逻辑蕴含

答案

参考答案:D

解析:[命题目的] 本题主要考查了对函数依赖的几个推理规则。 [解题要点] 自反律:若Y

X

U,则X→Y为F所逻辑蕴含;增广律:若X→Y为F所逻辑蕴含,且Z

U,则XZ→YZ为F所逻辑蕴含;传递律:若X→Y及Y→Z为F所逻辑蕴含,则X→Z为F所逻辑蕴含。 [考点链接] 掌握合并规则、伪传递规则、分解规则。

阅读理解

阅读理解。

     UK schoolchildren score lower than their equals (同龄人) in nine other countries in world knowledge,

according to the British Council. In a survey measuring the international viewpoint of young people around

the world, British pupils scored slightly lower than those in the US and much lower than those in other

European countries.

     The survey asked 11 to 16-year-olds with household Intemet access in ten countries some questions to

learn their attitudes towards language learning and international affairs. Results were scored on an index of 

0 to 7. Nigeria came top of the table with 5.15, followed by India and Brazil. Within the UK, English

schootchildren (2.17) scored lowest compared with their counterparts in Scotland (2.35) ,Wales (2.43) and

Northern Ireland (2.26).

     British Council chief manager, Martin Davidson, said, "Our schoolchildren cannot afford to fall behind

the rest of the world. For the UK to compete in a global economy, it is vital that we encourage our young

people to have an interest in and engagement with the world around them." According to the research, UK

schoolchildren (32%) are the least likely to go out of their way to understand current events in the world.

More than twice as many Brazilian (69%) and German children (61%) said they would do so, compared

with a third of Scottish children.

     When asked whether they saw themselves as citizens of the world or of their own country, most of the

school children saw themselves first as world citizens. But children in the UK, US and Czech Republic saw

themselves more as citizens of their own country.

     Under three-quarters (70%) of UK, school children felt that it was important to speak a foreign language

for their future work (65% in Scotland). This compared with 100% of school children in Saudi Arabia, 97%

in Brazil and India, 85% in China and 73% in America. The foreign language that the UK school children felt

was most important to learn was French (40% of those naming a foreign language), followed by Spanish

(31%), German ( 8% ) and then Chinese (60%, rising to 9% in Scotland).

1. What does the underlined word "counterparts" in Paragraph 2 most probably mean? [ ]

A. Equals.

B. Students.

C. Parents.

D. Enemies.

2. What is the most important foreign language in the opinion of UK schoolchildren? [ ]

A. German.

B. Chinese.

C. French.

D. Spanish.

3. What is the British Council chief manager's attitude towards the survey results? [ ]

A. Enthusiastic.

B. Worried.

C. Excited.

D. Positive.

4. Which of the following would be the best title for the passage? [ ]

A. French: the most popular language.

B. Global awareness: an important matter.

C. British children lack global awareness.

D. A survey about British schoolchildren.

选择题