英语专四试题练习完形填空训练

英语专四试题练习完形填空训练2017

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　　part 1

　　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 B.intention C.reason D.modern

　　E. strongly F.figure G.come H.significant

　　I. exactly J.increase K.proposals L.turn

　　M. purposes N.varieties O.serious

　　参考答案

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

　　part 2

　　Leonardo da Vinci was the first man to suggest that growing trees add a new ring in their trunks each year. The 11 in these rings relates to the physical conditions which the tree experiences. Thus, trees grown in a 12 area and time each develop a pattern or configuration of their rings.

　　This 13 was of little significance until Andrew E. Douglas began to study tree rings in Arizona in 1900. Using a technique called cross dating, he was able to employ tree rings to the study of archaeological sites and date the ruins with 14 . Some were as old as 6700 B. C. ! This study of tree rings is called dendrochronology.

　　In time the cross dating was 15 by a carbon 14 process. This approach measured the amount of carbon 14 radiating from a piece of wood and 16 to determine the age of that wood. Further use of the carbon 14 technique has shown that the radiation process is more complex and less 17 than had been at first thought.

　　The most 18 aspect of tree ring research is now called

　　dendroclimatology. This 19 of the reconstruction of climates and climatic cycles and events from the evidence found in the tree rings. From this it is hoped that a 20 of drought cycles can be determined in the American Southwest. Such information will be of great help in determining the life and ecology of that region of the United States.

　　A. thus B.model C.variation D.concept

　　E. accuracy F.exciting G.consists H.given

　　I. proposition J.composes K.further L.pattern

　　M. supplemented N.reliable O.excellent

　　参考答案

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

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