问题 单项选择题

下列概念中,不是数据库管理系统必须提供的数据控制功能的是( )。

A.安全性

B.完整性

C.移植性

D.一致性

答案

参考答案:C

解析:[分析] 数据库管理系统是数据库系统的核心,是对数据库进行管理的软件系统。完成对数据的科学组织、存储以及高效地获取和维护数据,它为用户或应用程序提供了访问数据库中的数据和对数据的安全性、完整性、保密性、并发性等进行统一控制的方法。

阅读理解

阅读理解。

     One day, Allan and his friend Henry went swimming in a river. It was very hot. How happy they were in

the river! After they got out of the water, they played games in the sun for a while.   

     On their way back, Henry saw some flowers. He liked flowers very much and ran into the green field to

look at them. Now Allan was walking by himself.   

     Then he heard Henry calling out, "A snake (蛇)! Help!..."   

     "What's wrong with you?" asked Allan.   

      "A snake bit (咬) me in the leg. Come here!"   

      Allan ran over and saw a small red wound (伤口) on Henry' s leg.   

      "The snake was in the grass. I didn't see it."  

      "Sit down quickly"! Allan told Henry.   

      Allan put his mouth at the little red wound and began to suck (吸) at it. In this way he saved (挽救)

Henry's life. "Oh, Allan, it's very kind of you to help me."   

      "That's all right. We are friends and we must always help each other."

1. It was _______ when-Allan and Henry went out.   

A. hot

B. cold

C. raining

D. wet

2. After swimming, they played in the sun ________.   

A. the whole morning

B. for 2 hours   

C. long

D. for a while

3. On their way home, ________ got something wrong with his   

A. Allan; leg

B. Allan; head   

C. Henry; leg

D. Henry; head

4. Henry and Allan are ________.   

A. workers

B. good friends   

C. brothers

D. farmers

5. Which of the following (下面的) is true?   

A. Henry went to look at the flowers with Allan.   

B. Allan saved Henry' s life.   

C. Allan saw the snake.   

D. They ran to the hospital at once.

单项选择题