问题 单项选择题

信元交换是ATM通信中使用的交换方式,下面有关信元交换的叙述中,错误的是______。

A.信元交换是一种无连接的通信方式
B.信元交换采用固定长度的数据包作为交换的基本单位
C.信元交换可以采用硬件电路进行数据转发
D.信元交换是一种采用统计时分多路复用技术进行数据传输的方式

答案

参考答案:A

解析: 信元交换又叫异步传输模式(ATM),是一种面向连接的快速分组交换技术,它是通过建立虚电路来进行数据传输的。ATM作为B-ISDN的核心技术,特别适合高宽带和低时延应用。ATM技术的重要特征有信元传输、面向连接、统计时分多路复用和服务质量。ATM的基本传输单位是信元,信元是具有固定长度的分组。ATM提供的服务是面向连接的,通过虚电路传送数据。ATM采用统计时分多路复用方式将来自不同信息源的信元汇集到一起,采用统计时分多路复用方式有很大的灵活性。

阅读理解

(C)

Driving a car at high speed along a highway seems to be fun. You need only to follow the bright traffic signs beside the highways and it will take you to where you wish.

But to a London taxi driver, driving is not an easy job. A taxi driver has to have not only good driving skills but also a good knowledge of the city of a London, from the smallest lane to the most popular bar around. He has to be at the service of all kinds of passengers at all times.

A certain London taxi driver told of his job as follows.

During the night it is quite usual for him to stop two or three times for some refreshments (点心). He said. "I never drink when I'm working ---- I would lose my licence."

He normally goes home between 2 and 3 O'clock in the night, There are times he has to stay longer and try to make more runs. He said, "That's the worst thing about working for yourself. If you don't make the money, no one is going to give it to you."

London taxi drivers not only ‘take' but also ‘give' , Every summer hundreds of children from London will go for a day at the sea--- by taxi! Their rides are paid by the taxi drivers, and these fares all go to the ‘London Taxi Fund for Underprivileged Children.' At the sea. they are met by the mayor, and a lunch party is also held in honour of the taxi drivers and the children. After a happy day running around the sea beaches and visiting the market, the children go home again-- by taxi, and free of charge, of course!

62. To be a London driver is not easy because ______.

A. he has to follow the bright traffic signs

B. he has to have good driving skills and know all the places in the city

C. he has to serve all kinds of passengers at all times

D. both B. and C

63. The London taxi drivers _______.

A. work hard because on one would give them money for doing nothing

B. never stop driving in the city

C. only work between 2 and 3 o'clock in the night

D. are very rich

64. The author of the passage says that _______.

A. the taxi driver works longer than is necessary

B. the more runs the taxi driver makes, the more he gets

C. the taxi driver doesn't like to work for others

D. the taxi drivers in the city go to the seaside to attend a party every year.

65. London taxi driver _______.

A. take money because they have to pay for the children's ride

B. go to the sea for a day in the summer

C. pay the fares for the poor children to the sea for a day once every year

D. give the poor children a free ride for a day at the sea once every year

66. The underlined words Underprivileged Children mean children _______.

A. of low income families                            B. who like to travel in taxi

C. who wish to go to sea but have no money      D. from London

单项选择题