问题 单项选择题

下列关于集线器的描述中,错误的是______。

A.集线器基于MAC地址完成数据帧转发
B.连接到集线器的结点发送数据时采用CSMA/CD算法
C.通过在网络链路中串接一个集线器可以监听该链路中的数据包
D.连接到一个集线器的所有结点共享一个冲突域

答案

参考答案:A

解析: 集线器工作于物理层,以广播的形式进行数据转发。结点通过双绞线连接到一个集线器上,当其中一个结点发送数据的时候,所有结点都可以收到消息,即链路中串接集线器可以监听该链路中的数据包,且每次只能有一个结点能够发送数据,而其他的结点都处于接收数据的状态。连接到集线器的所有结点共享一个冲突域,这些结点执行CSMA/CD介质访问控制方法。

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Is losing weight as simple as doing a 15-minute writing exercise? In a new study, women who wrote about their most important values, like close relationships or religion, lost more weight over the next few months than women who didn't. "We have this need to feel self-integrity (正直,诚实),” says Christine Logel of the University of Waterloo. "When something threatens your sense that you're a good person, like failing a test, we can buffer(缓冲) that self-integrity by reminding ourselves how much we love our children, for example".

For this study, the researchers recruited 45 female undergraduates, of whom 58% were overweight. Each woman was weighed, and was then given a list ofimportant values, like creativity, music or relationships with friends and family members. Each woman ranked the values in order of how important they were to her. Then half the women were told to write for 15 minutes about the value that was most important to her. The other half, a control group, were told to write about why a value far down on their list might be important to someone else.

The women came back months later to be weighed again. Women who had written about an important value lost an average of 3.41 pounds, while women in the control group gained an average of 2.76 pounds.

"How we feel about ourselves can have a big effect," Logel says. Maybe when one of the women who wrote about an important value went home that night, she felt good about herself and didn't eat to make herself feel better. Over a few months, that could make a real difference in her life,

小题1:How can a 15-minute writing exercise ofimportant values affect people?

A.They will feel proud of themselves and gain weight gradually.

B.They may feel good about themselves and then eat less than usual.

C.They may continue writing and decide to become a professional writer.

D.They will never have meals at night to make themselves lose weight.小题2:What were the females required to do in the study?

A.Only the control group was given a list ofimportant values.

B.Both groups ranked the values in order of importance to them.

C.Each woman was weighed three times in the process of the study.

D.The overweight women wrote about the value most important to them.小题3:Which of the following persons may lose weight according to the new study?

A.Mary who wrote about her own adventure.

B.Catherine who described her illness in her writing.

C.Shirley who wrote how much she loved her children.

D.Alice who complained her boss in her diary.小题4:Which of the following might be the best title for the passage?

A.Writing Benefits Women a Lot

B.Losing Weight Is Very Simple

C.Writing Contributes to Losing Weight

D.Women Values Losing Weight