托福阅读练习4Word文档格式.docx

1、of the answer became clear: the electrons are produced in jets that are shot out inopposite directions from the center of a galaxy. Remarkably narrow and highly directional,（20） the jets move outward at speeds close to the speed of light. When the jets strike thehighly rarefied gas that permeates in

2、tergalactic space, the fast-moving electrons losetheir highly directional motion and form vast clouds of radio-emitting gas.Cosmic jets have ranked among the hottest topics of astronomical research in recentyears as astronomers strive to understand where they come from. Why should a galaxy（25） eject

3、 matter at such tremendous speeds in two narrow jets? And why are such jets notseen in the Milky Way?1. The word celestial in line 1 could best be replaced by（A） visible（B） astronomical（C） glowing（D） scientific2. The word entities in line 4 is closest in meaning to（A） factors （B） processes（C） object

4、s （D） puzzles3. In the first paragraph, the author describes objects in the universe in terms of their（A） color （B） origin（C） location （D） shape4. Which of the following is the best representation of the clouds of radio emission described in the first paragraph?（A） （B）（C）（D）5. According to the passa

5、ge, scientists do not fully understand why double radio sources（A） have not eventually disappeared（B） cannot be observed with a telescope（C） are beginning to slow down（D） are not as big as some planets and stars6. The word their in line 22 refers to（A） speeds（B） directions（C） electrons（D） clouds7. A

6、ccording to the passage, what happens when electrons and gas collide in space?（A） The gas becomes more condensed.（B） The gas becomes less radiated.（C） The electrons disperse.（D） The electrons become negatively charged.8. The author suggests that astronomers consider the study of cosmic jets to be（A）

7、 an obsolete scientific field（B） an unprofitable venture（C） an intriguing challenge（D） a subjective debate9. In what lines does the passage compare the size of double radio sources with that of other galaxies?（A） Lines 4-6 （B） Lines 12-14（C） Lines 19-20 （D） Lines 23-2410. Where in the passage does t

8、he author mention a technology that aided in the understanding of double radio sources?（A） Lines 2 （B） Line 7（C） Line 17 （D） Line 2111. The paragraph following the passage most likely discusses（A） specific double radio sources（B） an explanation of the synchrotron process（C） possible reasons for the

9、presence of cosmic jets（D） the discovery of the first double radio sourcesPassage 2Botany, the study of plants, occupies a peculiar position in the history of human knowledge.For many thousands of years it was the one field of awareness about which humans had anything more than the vaguest of insigh

10、ts. It is impossible to know today just what our Stone Age ancestors knew about plants, but from what we can observe of preindustrial societies that （5） still exist, a detailed learning of plants and their properties must be extremely ancient. This is logical. Plants are the basis of the food pyrami

11、d for all living things, even for other plants. They have always been enormously important to the welfare of people, not only for food, but also for clothing, weapons, tools, dyes, medicines, shelter, and a great many other purposes. Tribes living today in the jungles of the Amazon recognize literal

12、ly hundreds of plants and know （10） many properties of each. To them botany, as such, has no name and is probably not even recognized as a special branch of knowledge at all. Unfortunately, the more industrialized we become the farther away we move from direct contact with plants, and the less disti

13、nct our knowledge of botany grows. Yet everyone comesunconsciously on an amazing amount of botanical knowledge, and few people will fail to （15） recognize a rose, an apple, or an orchid. When our Neolithic ancestors, living in the Middle East about 10,000 years ago, discovered that certain grasses c

14、ould be harvested and their seedsplanted for richer yields the next season, the first great step in a new association of plants and humans was taken. Grains were discovered and from them flowed the marvel of agriculture:cultivated crops. From then on, humans would increasingly take their living from

15、 the controlled（20） production of a few plants, rather than getting a little here and a little there from many varieties that grew wild-and the accumulated knowledge of lens of thousands of years of experience and intimacy with plants in the wild would begin to fade away.12. Which of the following a

16、ssumptions about early humans is expressed in the passage?（A） They probably had extensive knowledge of plants.（B） They divided knowledge into well-defined fields. （C） They did not enjoy the study of botany. （D） They placed great importance on ownershipof property. 13. The word peculiar in line 1 is

17、closest in meaning to （A） clear （B） large （C） unusual （D） important 14. What does the comment This is logical in lines 5-6 mean?（A） There is no clear way to determine the extent of our ancestors knowledge of plants. （B） It is not surprising that early humans had a detailed knowledge of plants.（C） It

18、 is reasonable to assume that our ancestors behave very much like people in preindustrial societies. （D） Human knowledge of plants is well organized and very detailed. 15. The phrase properties of each in line 10 refersto each （A） tribe （B） hundred （C） plant （D） purpose 16. According to the passage,

19、 why has general knowledge of botany declined?（A） People no longer value plants as a useful resource. （B） Botany is not recognized as a special branch of science. （C） Research is unable to keep up with the increasing number of plants. （D） Direct contact with a variety, of plants has decreased. 17. I

20、n line 15, what is the authors purpose in mentioning a rose, an apple, or an orchid?（A） To make the passage more poetic （B） To cite examples of plants that are attractive （C） To give botanical examples that most readers will recognize （D） To illustrate the diversity of botanical life 18. According t

21、o the passage, what was the first great step toward the practice of agriculture?（A） The invention of agricultural implements and machinery （B） The development of a system of names for plants （C） The discovery of grasses that could be harvested and replanted （D） The changing diets of early humans 19.

22、 The word controlled in line 19 is closest in （A） abundant （B） managed （C） required （D） advanced 20. The relationship between botany and agricultureis similar to the relationship between zoology （the study of animals ）（A） deer hunting （B） bird watching （C） sheep raising （D） horseback riding 21. Wher

23、e in the passage does the author describe the benefits people derive from plants?（A） Line 1（B） Lines 6-8（C） Lines 10-11（D） Lines 13-15PASSAGE 3If the physical barriers of the plant are breached, then preformed chemicals may inhibit or kill the intruder, and plant tissues contain a diverse array of t

24、oxic or potentially toxic substances, such as resins, tannins, glycosides, and alkaloids, many of which are highly effective deterrents to insects that feed on plants. The success of the Colorado beetle in infesting potatoes, for example, seems to be correlated with its high tolerance to alkaloids t

25、hat normally repel potential pests. Other possible chemical defenses, while not directly toxic to the parasite, may inhibit some essential step in the establishment of a parasitic relationship.22. Which of the following substances does the author mention as NOT necessarily being toxic to the Colorad

26、o beetle?（A） Resins（B） Tannins（C） Glycosides（D） AlkaloidsPASSAGE 4Each pueblo represented an astonishing amount of well-organized labor. Using only stone and wood tools, and without benefit of wheels or draft animals, the builders quarried ton upon ton of sandstone from the canyon walls, cut it into

27、 small blocks, hauled the blocks to the construction site, and fitted them together with mud mortar. Roof beams of pine or fir had to be carried from logging areas in the mountain forests many kilometers away. Then, to connect the pueblos and to give access to the surrounding tableland, the architects laid out a system of public roads with stone staircases for ascending cli