问题 填空题

在关系数据库中,把数据表示成二维表,每一个二维表称为 【4】

答案

参考答案:关系

解析: 在关系数据库中,一个关系的逻辑结构就是一张二维表。这种用二维表的形式表示实体和实体间联系的数据模型称为关系数据模型。

阅读理解

阅读理解。

    When you are in England, you must be careful in the streets because the traffic drives on the left. Before

you cross the street, you must look to the right and then the left.

    If the traffic lights are green, the traffic can go. People on foot mustn't cross.

    In the morning and in the evening when people go to or come from work, the streets are busy. The traffic

is the most dangerous then.

    When you go by bus in England, you have to be careful too. Always remember the traffic moves on the

left. So you must be careful. Have a look first or you will go the wrong way.

    In many English cities, there are big buses with two floors. From there you can see the city very well. It's

very interesting.

1. The traffic in England is           that in china. [ ]

A. the same as

B. different from

C. better than

D. worse than

2. You can cross the road when _____.[ ]

A. there is little traffic

B. the traffic lights are green

C. you look to the right

D. the traffic lights are red

3. When are there many buses, cars and people in the streets? [ ]

A. In the morning when people go to work.

B. At noon when people are having lunch.

C. In the evening when people come back from work.

D. Both A and C.

4. If you ride a bicycle in England, you must go _____. [ ]

A. on the left side of the road

B. on the right side of the road

C. in the middle of the road

D. very fast

5. The visitors to English cities usually like to           when they go by bus. [ ]

A. ride a bike

B. take a car

C. sit on the second floor

D. sit on the first floor

判断题