Meteorite Impact and Dinosaur

1、paragraph 1：1. The word pose in the passage is closest in the meaning to _ .A ClaimB ModelC AssumeD Presentparagraph 2：2. In paragraph 2, why does the author include the information that dinosaurs had flourished for tens of millions of years and then suddenly disappeared?A To support the claim that

2、the mass extinction at the end of the Cretaceous is the best-documented of the dozen or so mass extinctions in the geological record.B To explain why as many as half of the species on Earth at the time are believed to have become extinct at the end of the Cretaceous.C To explain why paleontologists

3、have always been intrigued by the mass extinction at the end of the Cretaceous.D To provide evidence that an impact can be large enough to disturb the environment of the entire planet and cause an ecological disaster.paragraph 3：3. Which of the following can be inferred from paragraph 3 about the lo

4、cation of the meteorite impact in Mexico?A The location of the impact site in Mexico was kept secret by geologists from 1980 to 1990.B It was a well-known fact that the impact had occurred in the Yucat region.Meteorite Impact and Dinosaur ExtinctionThere is increasing evidence that the impacts of me

5、teorites have had important effects on Earth, particularly in the field of biological evolution. Such impacts continue to pose a natural hazard to life on Earth. Twice in the twentieth century, large meteorite objects are known to have collided with Earth.If an impact is large enough, it can disturb

6、 the environment of the entire Earth and cause an ecological catastrophe. The best-documented such impact took place 65 million years ago at the end of the Cretaceous period of geological history. This break in Earths history is marked by a mass extinction, when as many as half the species on the pl

7、anet became extinct. While there are a dozen or more mass extinctions in the geological record, the Cretaceous mass extinction has always intrigued paleontologists because it marks the end of the age of the dinosaurs. For tens of millions of years, those great creatures had flourished. Then, suddenl

8、y, they disappeared. The body that impacted Earth at the end of the Cretaceous period was a meteorite with a mass of more than a trillion tons and a diameter of at least 10 kilometers. Scientists first identified this impact in 1980 from the worldwide layer of sediment deposited from the dust cloud

9、that enveloped the planet after the impact. This sediment layer is enriched in the rare metal iridium and other elements that areC Geologists knew that there had been an impact before they knew where it had occurred.D The Yucat region was chosen by geologists as the most probable impact site because

10、 of its climate.4. According to paragraph 3, how did scientists determine that a large meteorite had impacted Earth?A They discovered a large crater in the Yucat region of Mexico.B They found a unique layer of sediment worldwide.C They were alerted by archaeologists who had been excavating in the Yu

11、cat region.D They located a meteorite with a mass of over a trillion tons.paragraph 4:5. The word excavating in the passage is closest in the meaning to _ .A Digging outB ExtendingC DestroyingD Covering up6. The word consumed in the passage is closest in the meaning to _.A Changed B Exposed C Destro

12、yedD Covered7. According to paragraph 4, all of the following statements are true of the impact relatively abundant in a meteorite but very rare in the crust of Earth. Even diluted by the terrestrial material excavated from the crater, this component of meteorites is easily identified. By 1990 geolo

13、gists had located the impact site itself in the Yucat region of Mexico. The crater, now deeply buried in sediment, was originally about 200 kilometers in diameter. This impact released an enormous amount of energy, excavating a crater about twice as large as the lunar crater Tycho. The explosion lif

14、ted about 100 trillion tons of dust into the atmosphere, as can be determined by measuring the thickness of the sediment layer formed when this dust settled to the surface. Such a quantity of material would have blocked the sunlight completely from reaching the surface, plunging Earth into a period

15、of cold and darkness that lasted at least several months. The explosion is also calculated to have produced vast quantities of nitric acid and melted rock that sprayed out over much of Earth, starting widespread fires that must have consumed most terrestrial forests and grassland. Presumably, those

16、environmental disasters could have been responsible for the mass extinction, including the death of the dinosaurs.at the end of the Cretaceous period EXCEPT: _.A A large amount of dust blocked sunlight from Earth.B Earth became cold and dark for several months.C New elements were formed in Earths cr

17、ust.D Large quantities of nitric acid were produced.paragraph 5:8. The phrase tentatively identified in the passage is closest in the meaning to _.A Identified after careful studyB Identified without certaintyC Occasionally identifiedD Easily identifiedparagraph 6:9. The word perspective in the pass

18、age is closest in the meaning to _.A Sense of valuesB Point of viewC Calculation D Complication 10. Paragraph 6 supports which of the following statements about the factors that are essential for the survival of a species?A The most important factor for the survival of a species is its ability toSev

19、eral other mass extinctions in the geological record have been tentatively identified with large impacts, but none is so dramatic as the Cretaceous event. But even without such specific documentation, it is clear that impacts of this size do occur and that their results can be catastrophic. What is

20、a catastrophe for one group of living things, however, may create opportunities for another group. Following opportunities for another group. Following each mass extinction, there is a sudden evolutionary burst as new species develop to fill the ecological niches opened by the event.Impacts by meteo

21、rites represent one mechanism that could cause global catastrophes and seriously influence the evolution of life all over the planet. According to some estimates, the majority of all extinctions of species may be due to such impacts. Such a perspective fundamentally changes our view of biological ev

22、olution. The standard criterion for the survival of a species is its success in competing with other species and adapting to slowly changing environments. Yet an equally important criterion is the ability of a species to survive random global ecological catastrophes due to impacts. compete and adapt

23、 to gradual changes in its environment.B The ability of a species to compete and adapt to a gradually changing environment is not the only ability that is essential for survival.C Since most extinctions of species are due to major meteorite impacts, the ability to survive such impacts is the most im

24、portant factor for the survival of a species.D The factors that are most important for the survival of a species vary significantly from one species to another.paragraph 7:11. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect

25、choices change the meaning in important ways or leave out essential information.A Until recently, nobody realized that Earth is exposed to unpredictable violent impacts from space.B In the last few decades, the risk of a random violent impact from space has increased.C Since most violent events on E

26、arth occur randomly, nobody can predict when or where they will happen.D A few decades ago, Earth became the target of random violent events originating in outer space. 12. According to the passage, who conducted investigations about the current dangers posed by large meteorite impacts on Earth?A Pa

27、leontologistsEarth is a target in a cosmic shooting gallery, subject to random violent events that were unsuspected a few decades ago. In 1991 the United States Congress asked NASA to investigate the hazard posed today by large impacts on Earth. The group conducting the study concluded from a detail

28、ed analysis that impacts from meteorites can indeed be hazardous. Although there is always some risk that a large impact could occur, careful study shows that this risk is quite small.B GeologistsC The United States CongressD NASA13. Look at the four squares that indicate where the following sentenc

29、e can be added to the passage.This is the criterion emphasized by Darwins theory of evolution by natural selection. Where would the sentence best fit?14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choi

30、ces that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.Scientists have linked the mass extinction at the end of the Creta

31、ceous with a meteorite impact on Earth.Answer choicesA Scientists had believed for centuries that meteorite activity influenced evolution on Earth.B An iridium-enriched sediment layer and a large impact crater in the Yucat provide evidence that a large meteorite struck Earth about 65 million years ago.C The site of the large meteorite impact at the