问题 单项选择题

数据库的三级模式中, ( )是对数据库中全体数据的逻辑结构和特征的描述。

A.模式

B.外模式

C.内模式

D.子模式

答案

参考答案:A

解析:[分析] 模式也称逻辑模式或概念模式,它是数据库中全体数据的逻辑结构和特征的描述,是所有用户的公共数据视图,是数据库系统模式结构的中间层;外模式也称子模式或用户模式。

阅读理解

What do people do with their old, out of date but still useful computers? Most people don’t know how to deal with them. Many old computers are put away. Many more are simply thrown away as rubbish.

Finally, some companies are thinking of ways to bring down the number of old computers. Sony has agreed to help recycle old Sony products(产品). Dell, Hewlett Packard and other companies now also take back some old computers of their own brands.

In some countries, laws have been passed, too. Computer companies have to pay for collecting and recycling their used products. And 70% of computer waste must be recycled. The idea behind the laws is that computer companies themselves should pay for the cost. That will encourage them to make computers which are easier and cheaper to repair and upgrade(升级).

Yet many people are throwing away good computers, while others cannot afford them at all. Hundreds of organizations are working on this problem. They collect and repair old computers. Some also teach others how to repair computers. These repaired computers then go to schools, charities(慈善团体) or people who need them. Giving a used computer to one of these organizations can turn one person’s rubbish into someone else’s useful things and cut down waste, too.

根据短文内容,选择正确答案。(10分)

小题1:What do many people do with old computers?

A.They sell them.  B.They send them to others.    C.They stop using them.

小题2:How many computer companies are mentioned in the second paragraph?

A.One.             B.Two.                 C.Three.

小题3:According to the laws in some countries, computer companies must       .

A.recycle most of their products

B.collect all their used products

C.make more cheaper computers

小题4:What do the organizations do to solve the problem of old computers?

A.Help the computer companies to collect them.

B.Repair and send them to those who need them.

C.Help people to learn to use them.

小题5:What is the main idea of this passage?

A.Repairing old computers.

B.Encouraging to make cheap computers.

C.Recycling old computers.        

问答题 简答题