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宽带ISDN的业务分为两类，即【20】业务和发布型业务。

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[说明] 信息系统中包含了信息资源、技术设备、任何环境等诸多因素，系统的效率是通过信息的作用和方式表现出来的，而信息的作用又要通过人在一定的环境中，借助以计算机技术为主体的工具进行决策和行动表现出来的。因此信息系统的效能既有有形的，也有无形的；既有直接的，也有间接的；既有固定的，也有变化的。因此，信息系统的评价具有复杂性和特殊性。信息系统评价中有关经济效益的评价方法有哪几种

What are the fields that receive the most attention at the beginning of 21st century

Part A You will hear a talk on how to obtain information. As you listen, answer Questions 1 to 10 by circling True or False. You will listen to the talk ONLY ONCE. You now have 1 minute to read Questions 1 to 10. In Megan Mullen’s eyes, CE-ROMS or the internet can’t match the printed words in books.

A. 对
B. 错

Part AText 1 People in the United States are becoming more and more aware of the influence of the automobile on their lives. The automobile has an influence on social life, on the economy, and on the environment. It is particularly its influence on the environment that people are increasingly worrying about. It has become obvious that the automobile contributes to air and noise pollution, traffic congestion, urban decay, and suburban sprawl, and that it has kept mass transit systems from developing. People are not so aware, however, of the relation between the automobile and energy problems. In the past few years the country has had energy problems such as brownouts and blackouts, fuel shortages, rising fuel prices, and bad effects on the environment caused by producing energy and converting it from one form to another. These energy problems are in fact closely related to the automobile. An enormous amount of energy, supplied mainly by petroleum, is required by the automobile. In fact, the automobile is responsible for 25 percent of the total energy consumption in the United States. Gasoline is only part of the energy required. It also take energy to manufacture the automobile in the first place. Then it must be transported to dealers who advertise and sell it, all of which takes energy. Energy is also required to make replacement parts for automobile repair. Once the car is on the road, energy still must go into producing gasoline for it. Oil fields must be discovered. Oil must be pumped to the surface and refined. And think of the energy required annually to build and maintain highways and roads. All together the energy requirements of a car are about 50 percent for gasoline and 50 percent for all these other needs that we have just mentioned. The question is, what can we do about all this What can we do to lower this figure, to conserve energy resources so as to reduce air pollution and help solve both our energy and automobile problems The most important thing we can do is to promote changes in passenger transportation. Bicycles are 22 times as energy-efficient as cars, walking 18 times, buses almost 4 times, and railroads 2.5 times. Only airplanes are less energy-efficient than cars. If we promote such changes, we won’t only conserve energy. We will also reduce the crowding and noise in the cities and we can use land for parks instead of for parking lots. It will take time for such changes to come about. Fortunately the sale of bicycles is increasing. And one thing we can do immediately is to increase the energy-efficiency of cars by using smaller cars and carrying more passengers. These changes that have just been suggested will require other changes in our society too, which some people may resist. It will not be easy to make these changes. But consider the alternatives. Which of the following consumes most energy

A. Cars.
Buses.
C. Planes.
D. Trains.