问题 单项选择题

假定每一个信用卡客户具有唯一的客户号。如果实体“客户信息”属性依次为“客户号、客户姓名、证件号码、开卡时间、卡状态”,其中,一个客户可以有多个卡,每个卡对应唯一的客户号;实体“客户交易记录”属性依次为“客户号、交易日期、交易开始时间、交易结束时间,交易类型、交易结果、交易金额”,其中一个客户一天可以进行多个交易,但同一时间只能进行一个交易。那么,实体“客户信息”的主键是 (40) ,实体“客户交易记录”的主键是 (41) ,这两个实体型间 (42) 联系。

A.存在一对一
B.存在一对多
C.存在多对多
D.不存在

答案

参考答案:B

解析: 对于实体“客户信息”,由于不同人可能有相同的姓名,同一客户(证件号码)可以开立多个信用卡,而一个信用卡拥有唯一标识的客户号,所以只需要(也只能够)有客户号就可以唯一确定该实体的特定个体,即对于实体“客户信息”,属性“客户号”是它的主键。
对于实体“客户交易记录”,一张卡(客户号)在同一天可以进行多个交易,但同时只能进行一个交易,即A交易结束之前不能进行B交易,所以,需要由“客户号、交易日期、交易开始时间”来确定一个特定的交易记录。
实体“客户信息”与“客户交易记录”之间是一对多的联系。

阅读理解

Parents often believe that they have a good relationship(关系)with their teenagers. But last summer, Joanna and Henry noticed a change in their older son: suddenly he seemed to be talking more to his friends than to his parents. “The door to his room is always shut,” Joanna noted.

Tina and Mark noticed similar changed in their 14-year-old daughter. “She used to cuddle up (蜷伏) with me on the sofa and talk,” said Mark. “Now we joke that she does this only when she wants something. Sometimes she wants to be treated like a little girl and sometimes like a young lady.”

Before age 11, children like to tell their parents what’s on their minds. “In fact, parents are first on the list,” said Michael Riera, author of Uncommon Sense for Parents with Teenagers. “This completely changes during the teen years,” Riera explained. “They talk to their friends first, then maybe their teachers, and their parents last.”

Parents who know what’s going on in their teenagers’ lives are in the best position to help them. To break down the wall of silence, parents should create chances to understand what their children want to say, and try to find ways to talk and write to them. And they must give their children a mental break(休息), for children also need freedom, though young. Another thing parents should remember is that to be a friend, not a manager, with their children is a better way to know them.

小题1:“The door to his room is always shut” suggests that the son ______.

A.is always busy with his studies

B.doesn’t want to be disturbed

C.keeps himself away from his parents

D.begins to dislike his parents小题2: What troubles Tina and Mark most is that _____.

their daughter isn’t as lovely as before  

they can’t read their daughter’s mind exactly

they don’t know what to say to their daughter

their daughter talks with them only when she needs help

小题3: Which of the following best explains “the wall of silence” in the last paragraph?

A. Teenagers talk a lot with their friends

B. Teenagers do not want to understand their parents.

C. Teenagers do not talk much with their parents

D. Teenagers talk little about their own lives小题4:What can be learned from the passage?

A.  Parents are unhappy with their growing children.

Parents have suitable ways to talk with their teenagers

C.   Parents should be patient with their silent teenagers.

D.   Parents should try to understand their teenagers.

单项选择题 A1型题