问题 单项选择题

“年龄在18~25之间”这种约束是属于数据库当中的

A.原子性措施

B.一致性措施

C.完整性措施

D.安全性措施

答案

参考答案:C

解析:[命题目的] 对数据库各种特性必须有正确的理解。 [解题要点] 数据库的完整性是指数据的正确性和相容性(如学生的学号必须唯一,性别只能是女或男等),数据库是否具备完整性关系到数据库系统能否真实反映现实世界,因此维护数据库的完整性是非常重要的。 [考点链接] 数据库的各种特性及表达形式。

阅读理解

阅读理解。

     A year after graduation, I was offered a position teaching a writing class.Teaching was a profession I

had never seriously considered, though several of my stories had been published.I accepted the job

without hesitation, as it would allow me to wear a tie and go by the name of Mr Davis.My father went by

the same name, and I liked to imagine people getting the two of us confused."Wait a minute," someone

might say, "are you talking about Mr Davis the retired man, or Mr Davis the respectable scholar?"

     The position was offered at the last minute, and I was given two weeks to prepare, a period I spent

searching for a briefcase (公文包) and standing before my fulllength mirror, repeating the words, "Hello,

class, I'm Mr Davis." Sometimes I would give myself an aggressive voice.Sometimes I would sound

experienced.But when the day eventually came, my nerves kicked in and the true Mr Davis was there.I

sounded not like a thoughtful professor, but rather a 12yearold boy.

     I arrived in the classroom with paper cards designed in the shape of maple leaves.I had cut them myself out of orange construction paper.I saw nine students along a long table.I handed out the cards, and the

students wrote down their names and fastened them to their breast pockets as I required.

     "All right then." I said. "Okay, here we go."Then I opened my briefcase and realized that I had never

thought beyond this moment.I had been thinking that the students would be the first to talk, offering their

thoughts and opinions on the events of the day.I had imagined that I would sit on the edge of the desk,

overlooking a forest of raised hands.Every student would shout to be heard, and I would knock on

something in order to silence them.I would yell, “Calm down, you'll all get your turn.One at a time, one at a time!”

     A terrible silence ruled the room, and seeing no other options, I instructed the students to pull out their

notebooks and write a brief essay related to the theme of deep disappointment.

1. The author took the job to teach writing because _____.

A.he wanted to be respected

B.he had written some stories

C.he wanted to please his father

D.he had dreamed of being a teacher

2.What can we learn about the author from Paragraph 2?

A.He would be aggressive in his first class.

B.He was wellprepared for his first class.

C.He got nervous upon the arrival of his first class.

D.He waited long for the arrival of his first class.

3.Before he started his class, the author asked the students to _____.

A.write down their suggestions on the paper cards

B.cut maple leaves out of the construction paper

C.cut some cards out of the construction paper

D.write down their names on the paper cards

4.What did the students do when the author started his class?

A.They began to talk.  

B.They stayed silent.

C.They raised their hands.  

D.They shouted to be heard.

单项选择题