英语专四考试教材辅导练习2017

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The birth of computers has brought with it a new set of opportunities for mischief and crime. Today, computers are easy to come by and many people know how computer technology 11 . More importantly, the growing use of computer networks can multiply the violation of security, making large numbers of people more vulnerable than would be the case if they were using 12 , stand-alone computers.

What's more, computer experts agree that—despite recent widespread publicity-computer viruses are 13 one of the many computer security problems facing the nation.

The U. S. Defense Advanced Research Project Agency has requested that the Research Council's Science and Technology Board 14 the security problems posed by computer technology, see what 15 may already exist, review research efforts 16 at avoiding security problems in the future, and evaluate existing policies 17 to computer security. The study committee will examine the 18 of security for a broad spectrum of users, including the business, national security, and academic communities, as well as the 19 public.

David. Clark, senior research scientist, Laboratory for Computer Science, Massachusetts Institute of Technology, will chair the 20 of experts in electronic security, net-work security, computer law, software engineering ? and operating systems. The committee will also include computer users from the defense and banking industries.

A. only s tions ral

E. issue amentally ersal ss

I. aimed le ittee rates

M. relevant tion unity

　　参考答案

II. B 12. J 13. A 14. H 15. C 16. I 17. M 18. E 19. D 20. K

Sugar is so much a part of our modern life that we only really think about it when, for some 11 , we cannot obtain it. It has been known to man for at least 3,000 years, but has 12 into common use only in 13 times. Until quite recently it was considered as a medicine and as a luxury for the very rich only.

Sugar is, then, 14 to our civilization. But what 15 is it? Of course, most of us recognize sugar immediately as the sweet material which we put in coffee or cakes. This common form of sugar is derived from two plants: the sugar cane (a type of grass which grows to a height of twenty feet) and the sugar beet (which grows under ground). But there are in fact many types of sugar, and the chemist recognizes hundreds of different 16 , each coming from a different source.

About 90% of the sugar is produced as food. Only 10% is used in industry for 17 other than food production. Yet sugar has great possibilities for use as the basis of chemicals. It can even be used for making plastics. In the future these potential uses will certainly be developed more than in the past.

There are many reasons why we should 18 the production of sugar. Most important is that it is one of the most highly concentrated of energy foods.

Thus sugar cane and beet produce an average of 7,000,000 calories per acre. In this way they have the advantage over potatoes which give only 4, 000, 000, while the 19 for wheat and beans is 2 ,000,000 each. So three acres of land growing wheat, beans and potatoes give only 20 more energy than one acre of sugar.

A. slightly ntion on rn

E. strongly re ificant

I. exactly ease osals

M. purposes eties ous

　　参考答案

II. C 12. G 13. D 14. H 15. I 16. N 17. M 18. J 19. F 20. A