单选题 A computer is a machine designed to perform work mathematically and to store and select in-formation that has been fed into it. It is run by either mechanical or electronic means. These ma-chines can do a great deal of complicated work in a very short time. A large computer, for exam-ple, can add or subtract nine thousand times a second, multiply a thousand times a second, or di-vide 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 ceils 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 pay-rolls, 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.
单选题 Computers are valuable to industry because they ______.
【正确答案】 B
【答案解析】文中第一段第三句说：“这些机器能够在极短的时间内处理大量的复杂工作。”文中第二段第三句说：“一个也许需要花费一个人两年时间才能解决的问题，而靠计算机只要一分钟就可以……”结合文中提供的其他信息，我们可以推断出正确答案为B。此题用排除法也可以找到答案。选项A、C、D在文中未涉及，均可排除，只有选项B是文章中所论述的内容。
单选题 The author calls the vacuum tubes the electronic computer"s ______.
【正确答案】 C
【答案解析】文中第二段第一句说：“电子计算机的心脏就在真空管或电子晶体管中。”由此可判断出选项C正确。
单选题 The speed with which an electronic computer works relies on ______.
【正确答案】 C
【答案解析】文中第二段第二句说：“它的电路的运转速度比人的大脑中的神经细胞的反应快1000倍。”由此可判断出C为正确答案。
单选题 The passage says that computer plays an essential part in ______.
【正确答案】 D
【答案解析】文中最后一段最后一句说：“计算机在世界上许多大小工厂的自动化中充当了关键的角色。”由此可判定选项D正确。
单选题 This passage indicates that human beings differ from computers in that human beings ______.
【正确答案】 A
【答案解析】此题是一道推断题。我们首先应结合文章的主题找出与问题相关的信息，然后进行深入细致的推断。文中第二段最后一句说：“一个也许需要花费一个人两年时间才能解决的问题，而靠计算机只要一分钟就可以解答出来。不过为了能正确地运行，计算机必须接受指令，也就是说必须给计算机编程序。”此句“but”一词后说必须给计算机编制程序，可以看出人正好与计算机相反，由此可推测出选项A正确。