问题 单项选择题

For (1) service, we need a virtual-circuit subnet. Let us see how that works. The idea behind virtual circuits is to avoid having to choose a new  (2) for every packet sent. Instead, when a connection is established, a route from the  (3) machine to the destination machine is chosen as part of the connection setup and stored in tables inside the (4) .That route is used for all traffic flowing over the connection, exactly the same way that the telephone system works. When the connection is released, the virtual circuit is also terminateD. With connection-oriented service, each packet carries an  (5) telling which virtual circuit it belongs to.

空白(1)处应选择()

A.connectionless

B.connection-oriented

C.datagram

D.telegram

答案

参考答案:B

解析:

实现面向连接的服务需要一个虚电路子网,下面看它如何工作。虚电路的主要思想是避免为每一个发送的分组都进行一次新的路由选择。事实上,在连接建立过程中,从源主机到目标主机的路由已经选定,并存储在路由器内部的路由表中。连接上的所有通信都使用这个路由,与电话系统的工作方式完全一样。当连接释放时,虚电路也终止了。在面向连接的服务中,每一个分组都含有一个标识符,用于表示该分组所属的虚电路号。

阅读理解

阅读表达。阅读下面短文并回答问题,然后将答案写到答题卡相应的位置上(请注意问题后的词数要

求)。

     [1]It is now possible to watch live sport on television on any day of the week, and the current amount of

reporting will undoubtedly increase further in years to come. This is certainly having an influence on the live

sports events themselves, and there are both benefits and shortcomings to this.

     [2]Why has there been such growth in televised sport? For one thing, with digital broadcasting, there are

now many more TV channels than there were even ten years ago. Moreover, sport has become an important

form of entertainment, appealing to both men and women.

     [3]When are the benefits of this state of affairs? One obvious advantage to the profession is the addition

of money provided by television companies. Large football clubs benefit financially from TV income and the

top players can command very large salaries. Less popular sports also receive money that can be used in

training and awareness-raising. What's more, there is a health benefit to some of the population, because

through televised sport, more people have become interested in actually playing sport.

     [4]However, _____ if so much sport is on television. Considering football again, many small clubs have

suffered financial losses recently, as they cannot compete with the large ones. There has been a general falling

in ticket sales, especially among smaller clubs. Fewer people attend live matches nowadays, preferring to

watch from the comfort of their living room. And ticket prices have risen greatly.

     [5]To sum up, while televised sport has created many opportunities and benefited certain people and clubs

very much, it has also been responsible for changing the nature of live sports events for ever.

1. What is the main idea of the text? (no more than 8 words)

    _______________________________________________________________________________

2. Complete the following statement with words from Paragraph 2. ( no more than 3 words)

    There has been a great increase in TV channels in the past few years with the help of

    _______________________________________________________________________________

3. Point out the advantage of televised sport which does not concern money in Paragraph3. (no more

    than 3 words)

    _______________________________________________________________________________

4. Fill in the blank in Paragraph 4 with proper words. (no more than 6 words)

    _______________________________________________________________________________

5. What does the word "it"  (Line2, Paragraph5) probably refer to? (no more than 3 words)

    _______________________________________________________________________________

单项选择题