问题 单项选择题

下列叙述中错误的是().

A.在数据库系统中,数据的物理结构必须与逻辑结构一致

B.数据库技术的根本目标是要解决数据的共享问题

C.数据库设计是指在已有数据库管理系统的基础上建立数据库

D.数据库系统需要操作系统的支持

答案

参考答案:A

解析:

数据库系统中,数据独立性是它的一个特点。一般分为物理独立性与逻辑独立性两级。物理独立性指数据的物理结构的改变,如存储设备的变换、存取方式的改变不影响数据库的逻辑结构,从而不引起应用程序的变化。逻辑独立性指数据库总体逻辑结构的改变,如修改数据模式、增加新的数据类型、改变数据联系等不需要相应修改应用程序。所以,在数据系统中,数据的物理结构并不一定与逻辑结构一致。

阅读理解

Mrs. Janes gave music lessons at a school.She had a good voice and enjoyed singing, except that some of her high tones sound like a gate that had forgotten to oil.Mrs. Janes knew her weakness well, and took every chance she could find to practise these high notes. As she lived in a small house, where she could not practise without disturbing the rest of the family, she usually went for long walks along the country roads whenever she had time and practised her high notes there.Whenever she heard a car or a person coming along the road, she stopped and waited until she could no longer be heard before she started practicing again, because she was a shy person.

One afternoon, a fast, opened car came up behind her so silently and so fast that she didn’t hear it until it was only a few yards from her.She was singing some of her highest and most difficult tones at that time and as the car passed, she saw an anxious expression came over the driver’s face.He stopped his car suddenly, jumped out and began to examine all his tyres carefully.

Mrs. Janes didn’t dare to tell him what the noise he had heard really was, so he got back into the car and drove off.

小题1:How did Mrs. Janes sing?

A.She sang well, but she didn’t practise singing hard.

B.She enjoyed singing, but she had a terrible voice.

C.She was a good singer, but she could not sing the high tones well.

D.She sang terribly, she was no singer at all.小题2:Why did she go for long walks along the country roads?

A.Because she enjoyed the country’s fresh air.

B.Because she was afraid to disturb the rest of the family.

C.Because she lived in a small house far away.

D.Because she was afraid to practise the high tones.小题3:Why did the driver stop his car suddenly and jump out of it?

A.Because he supposed something must have gone wrong with his car.

B.Because he was moved by the pretty voice of Mrs. Janes.

C.Because he wondered what had happened to Mrs. Janes.

D.Because he frightened by the terrible voice of Mrs. Janes.

判断题