GMAT PREP 08 答案.docx

1、GMAT PREP 08 答案PREP 1GWD30-Q11 to Q13: First identified in 1969, komatiites are Earths oldest known volcanic rocks and contain three times as much magnesium as do most volcanic rocks. This chemical composition suggests that komatiites formed from the hottest lava known ever to have erupted: a high c

2、oncentration of magnesium changes the physical properties of lava so that unusually high temperatures would be required for the lava to exist as a liquid. Komatiites discovery was surprising in light of then-current geological theories about magmas, molten rock that forms in the Earths mantle (the l

3、ayer beneath the crust) and composes volcanic lava eruptions. Prior to 1960, geologists Bowen and Hess disagreed over whether or not the very high temperatures needed to produce magmas rich in magnesium could have existed on Earth. Hess suggested that the presence of water, probably released from mi

4、nerals decomposing in the Earths mantle, might have meant that a high-magnesium magma could have existed at a lower temperature. But Bowen showed experimentally that the high temperatures were indeed necessary. By 1960, it was generally accepted that volcanic rocks with such high levels of magnesium

5、 could not exist, and thus the discovery of komatiites changed geologists assumptions about the characteristics of the Earths mantle around the time of the formation of komatiites, between 2.5 and 4 billion years ago.-Q11:Which of the following most accurately describes the organization of the passa

6、ge?A. Two divergent views of a scientific phenomenon are reconciled.B. A phenomenon is described and its scientific significance is discussed.C. The discovery of a scientific phenomenon is traced and its implications for further research are suggested.D. A long-standing scientific theory is examined

7、 and recently discovered evidence is shown to support it.E. The ways in which a particular geological phenomenon is exceptional are detailed and classified.-Q12:Information in the passage suggests which of the following concerning the Earths mantle 2.5 to 4 billion years ago?A. It contained magmas t

8、hat were more significantly affected by the decomposition of minerals than are current-day magmas.B. It contained a lower proportion of water that it contains today.C. Its characteristics were accurately described by both Bowen and Hess.D. Its temperature was sufficiently high to produce magmas with

9、 high magnesium content.E. Its total magnesium content then was roughly equivalent to its magnesium content today.-Q13:Which of the following most accurately states the main point of the passage?A. Komatiites provide information about rates of volcanic eruption between 2.5 and 4 billion years ago.B.

10、 Komatiites provide information about how the physical properties of lava in the Earths past compare with those of current-day lava.C. Komatiites provide evidence that undermines Bowens experimental conclusions regarding the temperatures at which lava exists as a liquid.D. Komatiites provide evidenc

11、e that has changed geologists ideas about the characteristics of the Earths mantle between 2.5 and 4 billion years ago.E. Komatiites provide evidence that water in the Earths mantle may have reduced the temperature required for lava to exist as a liquid.BQ33-Q36: TTGWD11-Q24 to Q27: Anole lizard spe

12、cies that occur together (sympatrically) on certain Caribbean islands occupy different habitats: some live only in the grass, some only on tree trunks, and some only on twigs. These species also differ morphologically: grass dwellers are slender with long tails, tree dwellers are stocky with long le

13、gs, twig dwellers are slender but stubby-legged. What is striking about these lizards is not that coexisting species differ in morphology and habitat use (such differences are common among closely related sympatric species), but that the same three types of habitat specialists occur on each of four

14、islands: Puerto Rico, Cuba, Hispaniola, and Jamaica. Moreover, the Puerto Rican twig species closely resembles the twig species of Cuba, Hispaniola, and Jamaica in morphology, habitat use, and behavior. Likewise, the specialists for other habitats are similar across the islands. The presence of simi

15、lar species on different islands could be variously explained. An ancestral species might have adapted to exploit a particular ecological niche on one island and then traveled over water to colonize other islands. Or this ancestral species might have evolved at a time when the islands were connected

16、, which some of these islands may once have been. After the islands separated, the isolated lizard populations would have become distinct species while also retaining their ancestors niche adaptations. Both of these scenarios imply that specialization to each niche occurred only once. Alternatively,

17、 each specialist could have arisen independently on each of the islands. If each type of specialist evolved just once, then similar specialists on different islands would be closely related. Conversely, if the specialists evolved independently on each island, then a specialist on one island would be

18、 more closely related to other types of anoles on the same islandregardless of their ecological niches than it would be to a similar specialist on a different island. Biologists can infer how species are related evolutionarily by comparing DNA sequences for the same genes in different species. Speci

19、es with similar DNA sequences for these genes are generally more closely related to each other than to species with less-similar DNA sequences. DNA evidence concerning the anoles led researchers to conclude that habitat specialists on one island are not closely related to the same habitat specialist

20、s elsewhere, indicating that specialists evolved independently on each island. - 33. The primary purpose of the passage is to A. describe some unusual features of anole lizard species B. account for a particular type of behavior found among anole lizard species C. contrast two types of evidence that

21、 have been used to support a particular hypothesis concerning anole lizard species D. explain how researchers resolved a particular scientific question concerning anole lizard species E. examine different explanations for a particular trait common to certain anole lizard species - 34. Which of the f

22、ollowing best describes the purpose of the sentence in lines 13-23 (“What is Jamaica”)? A. It raises a question about why coexisting anole lizard species occupy the different types of habitats mentioned in the first sentence. B. It introduces a fact about anole lizard species that the passage will g

23、o on to explore. C. It identifies a particular aspect of anole lizard behavior that distinguishes anoles from other lizard species. D. It explains why one aspect of anole lizard species habitat use has been difficult to account for. E. It points out a surprising relationship between morphology and h

24、abitat use that is explained in the concluding paragraph. - 35. It can be inferred form the passage that which of the following is true of the Cuban tree-dwelling anole lizard and the Jamaican tree-dwelling anole lizard? A. They share a morphology characterized by stocky bodies and long legs. B. The

25、y have bodies that are relatively slender compared to their stubby legs. C. They differ significantly form one another in size. D. They differ significantly from one another in behavior and habitat use. E. They are genetically closely related to one another. - 36. The passage suggests that if a gras

26、s-dwelling anole lizard species evolved on one island and then traveled over water to colonize a second island, the grass-dwelling anoles on the two islands would eventually A. develop very different DNA sequences B. develop into different species that are more distantly related to each other than t

27、o tree- and twig-dwelling anoles on their own islands C. come to differ significantly from one another in habitat use D. develop into different, but closely related, speciesE. evolve significant morphological differencesQ 19 AQ20 CGWD-12-Q35 to Q37: Many economists believe that a high rate of busine

28、ss savings in the United States is a necessary precursor to investment, because business savings, as opposed to personal savings, comprise almost three-quarters of the national savings rate, and the national savings rate heavily influences the overall rate of business investment. These economists fu

29、rther postulate that real interest ratesthe difference between the rates charged by lenders and the inflation rateswill be low when national savings exceed business investment (creating a savings surplus), and high when national savings fall below the level of business investment (creating a savings

30、 deficit ). However, during the 1960s real interest rates were often higher when the national savings surplus was large. Counter-intuitive behavior also occurred when real interest rates skyrocketed from 2 percent in 1980 to 7 percent in 1982, even though national savings and investments were roughl

31、y equal throughout the period. Clearly, real interest rates respond to influences other than the savings/investment nexus. Indeed, real interest rates may themselves influence swings in the savings and investment rates. As real interest rates shot up after 1979, foreign investors poured capital into the United States, the price of domestic goods increased prohibiti