问题 单项选择题

在计算机网络体系结构中,要采用分层结构的理由是( )。

A.可以简化计算机网络的实现

B.各层功能相对独立,各层因技术进步而做的改动不会影响到其他层,从而保持体系结构的稳定性

C.比模块结构好

D.只允许每层和其上、下相邻层发生联系

答案

参考答案:B

解析: 分层结构和模块结构相比,各具特点。计算机软件的模块结构使得软件的编制可以实现模块相对独立;只要对外功能不变,则模块内部的变化不影响其他模块;但是模块间可以相互调用,模块结构并不确定只允许每层和其上、下相邻层发生联系。而采用分层结构既具有模块结构的优点,又能保证只允许每层和其上、下相邻层发生联系,或者说,层次结构是一种特殊的模块化结构,核心内容是层间的相对独立性。

单项选择题
阅读理解

任务型阅读。请认真阅读下面短文,并根据所读内容在文章后表格中的空格里填上一个最恰当的单词。

注意:每个空格只填1个单词。

      This year, about 2,300 teenagers from all over the world will spend about 10 months in US homes. At the

same time about 1,300 American teenagers will go to other countries to learn new languages and learn the rest

of the world. 

      Here is a 2-way student exchange in action. Fred, 19, spent last year in Germany with George's family.

In turn, George's son Mike spent a year in Fred's home in America.

      Fred, a lively young man, knew little German when he arrived. But after 2 months of studying, the

language became easy for him. School was completely different from what he had expected and it was much

harder. Students rose respectfully when the teacher entered the room. They took 14 subjects instead of 6 that

were usually taken in the US.

      Family life, too, was different. The father's word was the law. All the activities were done with the family

rather than individually. Fred found the food to be too simple at first. He also missed having a car. 

     "Back home, you pick up some friends in a car and go out to have a good time. In Germany, you walk but

you soon learn to like it."

      At the same time, in America, Mike, a friendly German boy, was also forming his own ideas. "I suppose

I should criticize American schools." he says, "It is far too easy for our level but I have to say that I like it a

lot in Germany, we do nothing buy study. Here we take part in many other activities. I think that maybe

American schools are better in training their citizens. There ought to be some middle ground between the two."

      1______ between American school life and German school life Items (项目) American students German

students Class rules They don't have to stand up. They have to rise to show respect to their 2______. 3______

life They do their own things individually. They have to listen to their 4______. School 5______ They are very

6______ to learn. They are much more difficult. Going out They can 7______ cars. They have to 8______ all

the way. School activities They have 9______ other activities. They have to 10______ hard all the time.