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问题 单项选择题

信息系统的成本可分为固定成本和可变成本。（）属于固定成本，（）周于可变成本。

（）属于固定成本

A．硬件购置成本和耗材购置成本

B．软件购置成本和硬件购置成本

C．耗材购置成本和人员变动工资

D．开发成本和人员变动工资

答案

参考答案：B

多项选择题

Passage 1If you have never seen a power plant, you might find it hard to imagine how enormously complex the equipment is or how much heat is generated by the boilers or how much coal it takes to fuel the furnaces for just one day.During the course of a day, the boilers at one of our power plants, Morgantown, for example, can turn 24 million gallons of water into steam. That generating plant alone uses 9,900 tons of coal in its furnaces in just one day. Potomac Electric Power Company (PEPCO) uses so much coal that we have purchased two 80-car unit trains to facilitate the delivery process. And Morgantown alone can produce over 25 million kilowatthours of electricity in a single day’’s operation.Electricity is produced by spinning large magnets inside a coil of wire within the generator. The faster we spin the magnets, the higher will be the voltage of the electricity produced. Electricity leaves a PEPCO generator at between 13,800 and 24,000 volts.The next step in the process occurs when electricity passes through a transformer where the voltage is stepped up to continue on its journey. A transmission wire is like a small diameter pipe. Stepping up the voltage is like increasing water pressure, thus speeding the flow of energy through the system.Passage 2Because the aircraft industry needs ever-increasing quantities of aluminium plate, new equipment has been designed to automate the making of it. It includes a huge heat-treatment furnace, a crane that lifts hot metal plates without damaging them, and a computer system that can manage the complete flow of work.Five years ago, Europe’’s aircraft industry needed only 8,000 tonnes of aluminium plate a year for its products. Last year the figure reached 21,800 tonnes. By 2004 it should total 30,000 tonnes. Each airliner contains 180 tonnes of it. That is why the plant is being rebuilt to increase both the quality and the amount of its product.Aluminium is alloyed with other metals and cast into ingots, and the surface of the ingots is smoothed off. After pre-heating, it is rolled in a mill that can take 3.75-m-wide slabs. The new equipment can make the process more efficient and can produce a better product. For example, computers control the temperature of the hot plates, the rate at which they pass through the mill, the speed of cooling it with water, and so on.The new plant can handle twice the throughput of the one that it is replacing, thanks to the completely automated and computerized process.
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单项选择题

对提高全口义齿固位和稳定意义最小的是

A．准确印模
B．有利的磨光面形态
C．合理的排牙
D．尽量扩大基托面积
E．指导患者正确使用义齿
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