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  3. A computer is a machine designed to perform work mathematically and to store and select information that has been fed into it. I

A computer is a machine designed to perform work mathematically and to store and select information that has been fed into it. I

admin2009-02-10  43
问题      A computer is a machine designed to perform work mathematically and to store and select information that has been fed into it. It is nm by either mechanical or electronic means. These machines can do a great deal of complicated work in a very short time. A large computer, for example, can add or subtract nine thousand times a second, multiply a thousand times a second, or divide five hundred times a second. Its percentage of error is about one in a billion digits. It has been estimated that human beings making calculations average about one mistake per two hundred digits.
     The heart of an electronic computer lies in its vacuum tubes, or transistors. Its electronic circuits work a thousand times faster than the nerve cells in the human brain. A problem that might take a human being two years to solve can be solved by a computer in one minute, but in order to work properly, a computer must be given instructions--it must be programmed. Computers can be designed for many specialized purposes--they can be used to prepare payrolls, guide airplane flights, direct traffic, even to play chess. Computers play an essential role in modern automation in many plants and factories throughout the world.
The essential role played by computers lies in ______.
选项 A、automation processes
B、mathematical computations
C、traffic control
D、the development of mathematical theory
答案A
解析 文章最后一句说：Computers play in essential role in modern automation in many plants and factories throughout the world.在全世界的许多工厂里，计算机在现代自动化程序方面起着必不可少的作用。所以选项A正确。
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