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TPO20-30托福阅读修辞目的题集锦Paragraph1:ThestoryofthewestwardmovementofpopulationintheUnitedStatesis,inthemain,thestoryoftheexpansionofAmericanagriculture—ofthedevelopmentofnewareasfortheraisingoflivestockandthecultivationofwheat,corn,tobacco,andcotton.After1815improvedtransportationenabledmoreandmorewesternfarmerstoescapeaself-sufficientwayoflifeandenteranationalmarketeconomy.Duringperiodswhencommoditypriceswerehigh,therateofwestwardmigrationincreasedspectacularly.OldAmericaseemedtobebreakingupandmovingwestward,observedanEnglishvisitorin1817,duringthefirstgreatwaveofmigration.EmigrationtotheWestreachedapeakinthe1830's.Whereasin1810onlyaseventhoftheAmericanpeoplelivedwestoftheAppalachianMountains,by1840morethanathirdlivedthere.1.Whatisthepurposeofthestatement,“Whereasin1810onlyaseventhoftheAmericanpeoplelivedwestoftheAppalachianMountains,by1840morethanathirdlivedthere”?OToillustratethatgenerallypopulationshiftsoccurrapidlyOTocorrectamistakenimpressionofAmericanagriculturefrom1810to1840OToemphasizetherangeandspeedwithwhichthewestwardmigrationoccurredOTodemonstratedhowattractivetheAppalachianMountainsweretoAmericansParagraph2:PollensamplesfromfreshwaterlakesinSyriaandelsewheretellusforestcoverexpandedrapidlyattheendoftheIceAge,forthesouthwesternAsianclimatewasstillcoolerandconsiderablywetterthantoday.Manyareaswerericherinanimalandplantspeciesthantheyarenow,makingthemhighlyfavorableforhumanoccupation.About9000B.C.,mosthumansettlementslayintheareaalongtheMediterraneancoastandintheZagrosMountainsofIranandtheirfoothills.Somelocalareas,liketheJordanRivervalley,themiddleEuphratesvalley,andsomeZagrosvalleys,weremoredenselypopulatedthanelsewhere.Heremoresedentaryandmorecomplexsocietiesflourished.Thesepeopleexploitedthelandscapeintensively,foragingonhillslopesforwildcerealgrassesandnuts,whilehuntinggazelleandothergameongrassylowlandsandinrivervalleys.Theirsettlementscontainexoticobjectssuchasseashells,stonebowls,andartifactsmadeofobsidian(volcanicglass),alltradedfromafar.Thisconsiderablevolumeofintercommunityexchangebroughtadegreeofsocialcomplexityinitswake.2.Whydoestheauthormentionseashells,stonebowls,andartifactsmadeofobsidian?OTogiveexamplesofobjectsobtainedthroughtradewithothersocietiesOToillustratethekindsofobjectsthatarepreservedinacoolclimateOToprovideevidencethattheorganizationofworkwasspecializedOTogiveexamplesoftheartisticabilityoflocalpopulationsParagraph2:Thetermfossiloftenimpliespetrifaction,literallyatransformationintostone.Afterthedeathofanorganism,thesofttissueisordinarilyconsumedbyscavengersandbacteria.Theemptyshellofasnailorclammaybeleftbehind,andifitissufficientlydurableandresistanttodissolution,itmayremainbasicallyunchangedforalongperiodoftime.Indeed,unalteredshellsofmarineinvertebratesareknownfromdepositsover100millionyearsold.Inmanymarinecreatures,however,theskeletoniscomposedofamineralvarietyofcalciumcarbonatecalledaragonite.Althougharagonitehasthesamecompositionasthemorefamiliarmineralknownascalcite,ithasadifferentcrystalform,isrelativelyunstable,andintimechangestothemorestablecalcite.3.Whydoestheauthormentionaragoniteinthepassage?OToemphasizethatsomefossilsremainunalteredformillionsofyearsOTocontrastfossilformationinorganismswithsofttissueandinorganismswithhardshellsOToexplainthatsomemarineorganismsmustundergochemicalchangesinordertofossilizeOToexplainwhyfossilshellsaremorelikelytosurvivethanarefossilskeletonsParagraph3:Geothermalreservoirswithtemperaturesabove180°centigradeareusefulforgeneratingelectricity.Theyoccurprimarilyinregionsofrecentvolcanicactivityashot,dryrock;naturalhotwater;ornaturalsteam.Thelattertwosourcesarelimitedtothosefewareaswheresurfacewaterseepsdownthroughundergroundfaultsorfracturestoreachdeeprocksheatedbytherecentactivityofmoltenrockmaterial.Theworld'slargestsupplyofnaturalsteamoccursatTheGeysers,120kilometersnorthofSanFrancisco,California.Inthe1990senoughelectricitytomeetabouthalftheneedsofSanFranciscowasbeinggeneratedthere.Thisfacilitywastheninitsthirddecadeofproductionandwasbeginningtoshowsignsofdecline,perhapsbecauseofoverdevelopment.Bythelate1990ssome70geothermalelectric-generatingplantswereinoperationinCalifornia,Utah,Nevada,andHawaii,generatingenoughpowertosupplyaboutamillionpeople.Eighteencountriesnowgenerateelectricityusinggeothermalheat.4.Inparagraph3,whydoestheauthormentionthatinthe1990sTheGeyserswasinitsthirddecadeofproduction?OToprovidethehistoricalcontextofthegeothermalproductionofelectricityintheUnitedStatesOToimplythatTheGeyserswasthefirstgeothermalsitetobeputintoproductioninCaliforniaOTohelpexplainthesignsofdeclineshownbyTheGeysersOToexplainwhy70newgeothermalsiteswereputintoelectricityproductioninthelate1990sParagraph4:Itwouldappearthattheinstabilityoftheclimaticconditionsledpopulationsthathadoriginallybeennomadictosettledownanddevelopasedentarystyleoflife,whichledinturntopopulationgrowthandtotheneedtoincreasetheamountoffoodavailable.Farmingoriginatedintheseconditions.Lateron,itbecameverydifficulttochangebecauseofthesignificantexpansionofthesepopulations.Itcouldb