GMAT PREP 08 答案.docx

GMAT PREP 08 答案.docx

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GMATPREP08答案

PREP1

GWD30-Q11toQ13:

Firstidentifiedin1969,komatiitesareEarth’soldestknownvolcanicrocksandcontainthreetimesasmuchmagnesiumasdomostvolcanicrocks.Thischemicalcompositionsuggeststhatkomatiitesformedfromthehottestlavaknownevertohaveerupted:

ahighconcentrationofmagnesiumchangesthephysicalpropertiesoflavasothatunusuallyhightemperatureswouldberequiredforthelavatoexistasaliquid.

Komatiites’discoverywassurprisinginlightofthen-currentgeologicaltheoriesaboutmagmas,moltenrockthatformsintheEarth’smantle（thelayerbeneaththecrust）andcomposesvolcaniclavaeruptions.Priorto1960,geologistsBowenandHessdisagreedoverwhetherornottheveryhightemperaturesneededtoproducemagmasrichinmagnesiumcouldhaveexistedonEarth.Hesssuggestedthatthepresenceofwater,probablyreleasedfrommineralsdecomposingintheEarth’smantle,mighthavemeantthatahigh-magnesiummagmacouldhaveexistedatalowertemperature.ButBowenshowedexperimentallythatthehightemperatureswereindeednecessary.By1960,itwasgenerallyacceptedthatvolcanicrockswithsuchhighlevelsofmagnesiumcouldnotexist,andthusthediscoveryofkomatiiteschangedgeologists’assumptionsaboutthecharacteristicsoftheEarth’smantlearoundthetimeoftheformationofkomatiites,between2.5and4billionyearsago.

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Q11:

Whichofthefollowingmostaccuratelydescribestheorganizationofthepassage?

A.Twodivergentviewsofascientificphenomenonarereconciled.

B.Aphenomenonisdescribedanditsscientificsignificanceisdiscussed.

C.Thediscoveryofascientificphenomenonistracedanditsimplicationsforfurtherresearcharesuggested.

D.Along-standingscientifictheoryisexaminedandrecentlydiscoveredevidenceisshowntosupportit.

E.Thewaysinwhichaparticulargeologicalphenomenonisexceptionalaredetailedandclassified.

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Q12:

InformationinthepassagesuggestswhichofthefollowingconcerningtheEarth’smantle2.5to4billionyearsago?

A.Itcontainedmagmasthatweremoresignificantlyaffectedbythedecompositionofmineralsthanarecurrent-daymagmas.

B.Itcontainedalowerproportionofwaterthatitcontainstoday.

C.ItscharacteristicswereaccuratelydescribedbybothBowenandHess.

D.Itstemperaturewassufficientlyhightoproducemagmaswithhighmagnesiumcontent.

E.Itstotalmagnesiumcontentthenwasroughlyequivalenttoitsmagnesiumcontenttoday.

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Q13:

Whichofthefollowingmostaccuratelystatesthemainpointofthepassage?

A.Komatiitesprovideinformationaboutratesofvolcaniceruptionbetween2.5and4billionyearsago.

B.KomatiitesprovideinformationabouthowthephysicalpropertiesoflavaintheEarth’spastcomparewiththoseofcurrent-daylava.

C.KomatiitesprovideevidencethatunderminesBowen’sexperimentalconclusionsregardingthetemperaturesatwhichlavaexistsasaliquid.

D.Komatiitesprovideevidencethathaschangedgeologists’ideasaboutthecharacteristicsoftheEarth’smantlebetween2.5and4billionyearsago.

E.

KomatiitesprovideevidencethatwaterintheEarth’smantlemayhavereducedthetemperaturerequiredforlavatoexistasaliquid.

B

Q33-Q36:

TTGWD11-Q24toQ27:

Anolelizardspeciesthatoccurtogether（sympatrically）oncertainCaribbeanislandsoccupydifferenthabitats:

someliveonlyinthegrass,someonlyontreetrunks,andsomeonlyontwigs.Thesespeciesalsodiffermorphologically:

grassdwellersareslenderwithlongtails,treedwellersarestockywithlonglegs,twigdwellersareslenderbutstubby-legged.Whatisstrikingabouttheselizardsisnotthatcoexistingspeciesdifferinmorphologyandhabitatuse（suchdifferencesarecommonamongcloselyrelatedsympatricspecies）,butthatthesamethreetypesofhabitatspecialistsoccuroneachoffourislands:

PuertoRico,Cuba,Hispaniola,andJamaica.Moreover,thePuertoRicantwigspeciescloselyresemblesthetwigspeciesofCuba,Hispaniola,andJamaicainmorphology,habitatuse,andbehavior.Likewise,thespecialistsforotherhabitatsaresimilaracrosstheislands.Thepresenceofsimilarspeciesondifferentislandscouldbevariouslyexplained.Anancestralspeciesmighthaveadaptedtoexploitaparticularecologicalnicheononeislandandthentraveledoverwatertocolonizeotherislands.Orthisancestralspeciesmighthaveevolvedatatimewhentheislandswereconnected,whichsomeoftheseislandsmayoncehavebeen.Aftertheislandsseparated,theisolatedlizardpopulationswouldhavebecomedistinctspecieswhilealsoretainingtheirancestors’nicheadaptations.Bothofthesescenariosimplythatspecializationtoeachnicheoccurredonlyonce.Alternatively,eachspecialistcouldhavearisenindependentlyoneachoftheislands.

Ifeachtypeofspecialistevolvedjustonce,thensimilarspecialistsondifferentislandswouldbecloselyrelated.Conversely,ifthespecialistsevolvedindependentlyoneachisland,thenaspecialistononeislandwouldbemorecloselyrelatedtoothertypesofanolesonthesameisland—regardlessoftheirecologicalniches—thanitwouldbetoasimilarspecialistonadifferentisland.BiologistscaninferhowspeciesarerelatedevolutionarilybycomparingDNAsequencesforthesamegenesindifferentspecies.SpecieswithsimilarDNAsequencesforthesegenesaregenerallymorecloselyrelatedtoeachotherthantospecieswithless-similarDNAsequences.DNAevidenceconcerningtheanolesledresearcherstoconcludethathabitatspecialistsononeislandarenotcloselyrelatedtothesamehabitatspecialistselsewhere,indicatingthatspecialistsevolvedindependentlyoneachisland.

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33.Theprimarypurposeofthepassageisto

A.describesomeunusualfeaturesofanolelizardspecies

B.accountforaparticulartypeofbehaviorfoundamonganolelizardspecies

C.contrasttwotypesofevidencethathavebeenusedtosupportaparticularhypothesisconcerninganolelizardspecies

D.explainhowresearchersresolvedaparticularscientificquestionconcerninganolelizardspecies

E.examinedifferentexplanationsforaparticulartraitcommontocertainanolelizardspecies

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34.Whichofthefollowingbestdescribesthepurposeofthesentenceinlines13-23（“Whatis…Jamaica”）?

A.Itraisesaquestionaboutwhycoexistinganolelizardspeciesoccupythedifferenttypesofhabitatsmentionedinthefirstsentence.

B.Itintroducesafactaboutanolelizardspeciesthatthepassagewillgoontoexplore.

C.Itidentifiesaparticularaspectofanolelizardbehaviorthatdistinguishesanolesfromotherlizardspecies.

D.Itexplainswhyoneaspectofanolelizardspecies’habitatusehasbeendifficulttoaccountfor.

E.Itpointsoutasurprisingrelationshipbetweenmorphologyandhabitatusethatisexplainedintheconcludingparagraph.

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35.ItcanbeinferredformthepassagethatwhichofthefollowingistrueoftheCubantree-dwellinganolelizardandtheJamaicantree-dwellinganolelizard?

A.Theyshareamorphologycharacterizedbystockybodiesandlonglegs.

B.Theyhavebodiesthatarerelativelyslendercomparedtotheirstubbylegs.

C.Theydiffersignificantlyformoneanotherinsize.

D.Theydiffersignificantlyfromoneanotherinbehaviorandhabitatuse.

E.Theyaregeneticallycloselyrelatedtooneanother.

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36.Thepassagesuggeststhatifagrass-dwellinganolelizardspeciesevolvedononeislandandthentraveledoverwatertocolonizeasecondisland,thegrass-dwellinganolesonthetwoislandswouldeventually

A.developverydifferentDNAsequences

B.developintodifferentspeciesthataremoredistantlyrelatedtoeachotherthantotree-andtwig-dwellinganolesontheirownislands

C.cometodiffersignificantlyfromoneanotherinhabitatuse

D.developintodifferent,butcloselyrelated,species

E.evolvesignificantmorphologicaldifferences

Q19

A

Q20

C

GWD-12-Q35toQ37:

ManyeconomistsbelievethatahighrateofbusinesssavingsintheUnitedStatesisanecessaryprecursortoinvestment,becausebusinesssavings,asopposedtopersonalsavings,comprisealmostthree-quartersofthenationalsavingsrate,andthenationalsavingsrateheavilyinfluencestheoverallrateofbusinessinvestment.Theseeconomistsfurtherpostulatethatrealinterestrates—thedifferencebetweentherateschargedbylendersandtheinflationrates—willbelowwhennationalsavingsexceedbusinessinvestment（creatingasavingssurplus）,andhighwhennationalsavingsfallbelowthelevelofbusinessinvestment（creatingasavingsdeficit）.However,duringthe1960’srealinterestrateswereoftenhigherwhenthenationalsavingssurpluswaslarge.Counter-intuitivebehavioralsooccurredwhenrealinterestratesskyrocketedfrom2percentin1980to7percentin1982,eventhoughnationalsavingsandinvestmentswereroughlyequalthroughouttheperiod.Clearly,realinterestratesrespondtoinfluencesotherthanthesavings/investmentnexus.Indeed,realinterestratesmaythemselvesinfluenceswingsinthesavingsandinvestmentrates.Asrealinterestratesshotupafter1979,foreigninvestorspouredcapitalintotheUnitedStates,thepriceofdomesticgoodsincreasedprohibiti