托福模拟考试及答案解析12

托福模拟考试及答案解析（12）

（1~14/共54题乂却读理解

NeutronStars

Whilethelargeststarknowntomanisroughly2,000timesthediameteroftheEarth*ssun,

therearealsostarssotinythattheyarenolargerthanasmallmetropolitanarea.Theseare

neutronstars.Aneutronstarisextremelydenseandisessentiallythecorpseofagiantstarwhich

collapsedaftergoingsupernova.Despiteitssmallsize,aneutronstarhasamassgreaterthan

oneandahalftimesthatofthesun,isamongthehotteststarsinthegalaxy,andhasoneofthe

strongestmagneticfieldsofanyobjectinexistence.Wheneveraneutronstarforms,itbegins

spinningrapidly,whichcausestheelectromagneticenergyitemitstoappeartoblink,orpulse,to

observersontheEarth.Astronomerscallthesespinning,blinkingneutronstarspulsars.

Astarmustreachacertainsize—roughlyfourtoeighttimesthesizeofthesun-tobeableto

formaneutronstar.Starssmallerthanthattypicallybecomewhitedwarfswhentheycollapse

whilethoselargerthanthatnormallytransformintoblackholesuponcollapsing.Theformation

ofaneutronstaroccurswhenasupernovadestroysastar'souterlayeryetleavesthedensecore

intact.Thecenterofthestarisusuallycomprisedofiron,butotherelementsmaybepresentin

smalleramounts.Withthestar'souterlayersgone,nuclearfusionisnolongerpossible,which

resultsingravityhavingnocounterbalancingoutwardforce.Therefore,gravityactsstronglyon

thecoreandmakesitextremelydense.Asthisdensitygrowsinstrength,theelectronsand

protonsinthecore'satomsareforcedtogethertoformacoreofneutronsandneutrinos.The

neutronstarformsastructurewithdifferentlayers,muchlikeotherbodiesintheuniverse.Ifthe

neutronstarisrelativelyyoung,itisstillveryhot,soitssurfacemaybemoreliquidthansolid

whileitsinnercoreismuchdenserandmoresolidified.

Aneutronstar'stemperatureisatitsheightsoonafteritsbirth,butthestargraduallybegins

coolingoffasitbecomesolderonaccountofthelossofneutrinos,whichstartflyingoffthestar

assoonasitiscreated.Overtime,theseneutrinoscarryawayagreatamountofthestar'senergy,

soitstemperaturefallstoalevelapproximatelyhalfofwhatitwasatitsgenesis.Nevertheless,

evenafterthislossoftemperature,aneutronstarranksasoneofthehotteststarsinthe

universe.Inaddition,whenitforms,aneutronstarspinsatanextremelyhighrate—somewhere

betweensixtyand600timespersecond.Thishighrotationisexplainedbythelawof

conservationofangularmomentum,whichpointsoutthatanobjectrotatesatafasterratethe

moreitisdrawninonitself.Thisissimilartothewaythatafigureskaterbeginsspinningfaster

themomentthatshepullsherarmstowardherbody.

Theextremedensityofaneutronstarcreatesaverystrongelectromagneticfield,whichis

mostoftenobservedintheX-rayband.Thismagneticfieldisalignedalongadifferentaxisthan

thespinningmotionofthestar,soitislikealighthousebeamrotatinginspace.Ifthestaris

alignedintherightwaywiththeEarth,astronomersusingradiotelescopearrayscanobservethis

spinningmagneticfield.AstronomerJocelynBellfirstobservedthisphenomenonin1967,and

suchstarsweresooncalledpulsars.MostpulsarsemitelectromagneticenergyintheX-rayband,

butsomeemititinthevisiblelightbandaswellasthegammarayband.

Theseobservationsledtothediscoveryofmoreneutronstars—almostallofthempulsars—in

thefollowingdecades.Somearecalledmillisecondpulsarsbecauseofthefactthattheyrotateas

manyas700timespersecond.Atpresent,astronomershavediscoverednearly2,000neutron

stars;however,itisbelievedthatthenumberofneutronstarsisfargreatersinceallofthem

cannotbeobservedfromtheEarthbecausetheirrotatingmagneticfieldsaremisalignedwiththe

planet.Inaddition,asneutronstarsage,thespeedoftheirrotationdecelerates,preventingthem

frombeingdiscoveredaseasilyasmoreswiftlyrotatingneutronstars.

*Glossary

nuclearfusion:areactioninwhichthenucleioflightatomsunitetoformthenucleiofheavier

atoms

neutrino:amasslessornearlymasslesslepton,anelementarytypeofparticle

millisecond:onethousandthofasecond

第1题

NeutronStars

Whilethelargeststarknowntomanisroughly2,000timesthediameteroftheEarth'ssun,there

arealsostarssotinythattheyarenolargerthanasmallmetropolitanarea.Theseareneutron

stars.Aneutronstarisextremelydenseandisessentiallythecorpseofagiantstarwhich

collapsedaftergoingsupernova.Despiteitssmallsize,aneutronstarhasamassgreaterthan

oneandahalftimesthatofthesun,isamongthehotteststarsinthegalaxy,andhasoneofthe

strongestmagneticfieldsofanyobjectinexistence.Wheneveraneutronstarforms,itbegins

spinningrapidly,whichcausestheelectromagneticenergyitemitstoappeartoblink,orpulse,to

observersontheEarth.Astronomerscallthesespinning,blinkingneutronstarspulsars.

Thewordcorpseinthepassageisclosestinmeaningto

A.kernel

B.body

C.propellant

0.remains

第2题

Inparagraph1,allofthefollowingquestionsareansweredEXCEPT:

A.Whatcausesapulsartobehaveinitsparticularmanner?

B.Whataresomeoftheuniquefeaturespossessedbyaneutronstar?

C.Forwhatreasondosomegiantstarssuddenlybecomesupernovas?

D.HowmuchbiggerthantheEarth'ssunisthebiggestknownstarinthegalaxy?

第3题

Astarmustreachacertainsize—roughlyfourtoeighttimesthesizeofthesun—tobeableto

formaneutronstar.Starssmallerthanthattypicallybecomewhitedwarfswhentheycollapse

whilethoselargerthanthatnormallytransformintoblackholesuponcollapsing.Theformation

ofaneutronstaroccurswhenasupernovadestroysastar'souterlayeryetleavesthedensecore

intact.Thecenterofthestarisusuallycomprisedofiron,butotherelementsmaybepresentin

smalleramounts.Withthestar'souterlayersgone,nuclearfusionisnolongerpossible,which

resultsingravityhavingnocounterbalancingoutwardforce.Therefore,gravityactsstronglyon

thecoreandmakesitextremelydense.Asthisdensitygrowsinstrength,theelectronsand

protonsinthecore'satomsareforcedtogethertoformacoreofneutronsandneutrinos.The

neutronstarformsastructurewithdifferentlayers,muchlikeotherbodiesintheuniverse.Ifthe

neutronstarisrelativelyyoung,itisstillveryhot,soitssurfacemaybemoreliquidthansolid

whileitsinnercoreismuchdenserandmoresolidified.

*Glossary

nuclearfusion:areactioninwhichthenucleioflightatomsunitetoformthenucleiofheavier

atoms

neutrino:amasslessornearlymasslesslepton,anelementarytypeofparticle

Thewordcounterbalancinginthepassageisclosestinmeaningto

A.accelerating

B.offsetting

C.viable

0.positional

第4题

Inparagraph2,theauthorimpliesthattheEarth'ssun

A.isprobablygoingtobecomeapulsarbillionsofyearsinthefuture

B.hasacorethatiscomprisedofironandothersimilarheavyelements

C.lacksthesizethatisnecessaryforittobecomeasupernova

D.willstopundergoingnuclearfusionatsometimeinthefuture

第5题

Accordingtoparagraph2,aneutronstarisverycompactbecauseof

A.themannerinwhichgravityaffectsit

B.thevariouslayersthatarefoundinit

C.theactionsoftheprotonsandneutronsinitsatoms

D.thelackofnuclearfusioninitscore

第6题

Aneutronstar'stemperatureisatitsheightsoonafteritsbirth,butthestargraduallybegins

coolingoffasitbecomesolderonaccountofthelossofneutrinos,whichstartflyingoffthestar

assoonasitiscreated.Overtime,theseneutrinoscarryawayagreatamountofthestar'senergy,

soitstemperaturefallstoalevelapproximatelyhalfofwhatitwasatitsgenesis.Nevertheless,

evenafterthislossoftemperature,aneutronstarranksasoneofthehotteststarsinthe

universe.Inaddition,whenitforms,aneutronstarspinsatanextremelyhighrate-somewhere

betweensixtyand600timespersecond.Thishighrotationisexplainedbythelawof

conservationofangularmomentum,whichpointsoutthatanobjectrotatesatafasterratethe

moreitisdrawninonitself.Thisissimilartothewaythatafigureskaterbeginsspinningfaster

themomentthatshepullsherarmstowardherbody.

Thewordgenesisinthepassageisclosestinmeaningto

A.variance

B.average

C.appearance

D.birth

第7题

Inparagraph3,whydoestheauthormentionafigureskater?

A.Toarguethatastronomersdonotfullyunderstandtheactionsofneutronstars

B.Ibmakeacomparisonbetweentheactionsofthatindividualandaneutronstar

C.Toprovideamathematicalproofofthelawofconservationofangularmomentum

D.Tbexplainwhyneutronstarsdonotalwaysrotateatsuchgreatspeeds

第8题

Accordingtoparagraph3,whichofthefollowingistrueofaneutronstar?

A.Theconstantlossofneutrinosiswhatinducesthestartospinatsuchanextremelyfastrate.

B.Eventhoughitcangainenergyoverthecourseofitslife,itwillneverattainthehigh

temperaturesitinitiallyhad.

C.Despiteseeingitstemperaturedecreasebyhalf,itisstillhotterthanalmostanythingelsein

theuniverse.

D.ltcanrotateatspeedsmuchgreaterthanplanets,moons,asteroids,orothercelestialbodies

canachieve.

第9题

Theextremedensityofaneutronstarcreatesaverystrongelectromagneticfield,whichismost

oftenobservedintheX-rayband.Thismagneticfieldisalignedalongadifferentaxisthanthe

spinningmotionofthestar,soitislikealighthousebeamrotatinginspace.Ifthestarisaligned

intherightwaywiththeEarth,astronomersusingradiotelescopearrayscanobservethis

spinningmagneticfield.AstronomerJocelynBellfirstobservedthisphenomenonin1967,and

suchstarsweresooncalledpulsars.MostpulsarsemitelectromagneticenergyintheX-rayband,

butsomeemititinthevisiblelightbandaswellasthegammarayband.

Theworditinthepassagerefersto

A.thismagneticfield

B.adifferentaxis

C.thespinningmotion

D.thestar

第10题

Inparagraph4,theauthor'sdescriptionofpulsarsmentionswhichofthefollowing?

A.Theindividualcreditedwithidentifyingtheiruniquebehavior

B.Thestrengththattheirelectromagneticfieldscanattain

C.Thereasonthattheyemitenergyonuptothreedifferentbands

D.ThemannerinwhichpeopleontheEarthcanidentifythembyusingtelescopes

第11题

Theseobservationsledtothediscoveryofmoreneutronstars—almostallofthempulsars—in

thefollowingdecades.Somearecalledmillisecondpulsarsbecauseofthefactthattheyrotateas

manyas700timespersecond.Atpresent,astronomershavediscoverednearly2,000neutron

stars;however,itisbelievedthatthenumberofneutronstarsisfargreatersinceallofthem

cannotbeobservedfromtheEarthbecausetheirrotatingmagneticfieldsaremisalignedwiththe

planet.Inaddition,asneutronstarsage,thespeedoftheirrotationdecelerates,preventingthem

frombeingdiscoveredaseasilyasmoreswiftlyrotatingneutronstars.

*Glossary

millisecond:onethousandthofasecond

Whichofthefollowingcanbeinferredfromparagraph5aboutmillisecondpulsars?

A.Mostofthepulsarsthathavebeendiscoveredaremillisecondpulsars.

B.Astronomersbelievethereareatleast2,000ofthemintheEarth'sgalaxy.

C.Theyrotateatsuchquickspeedsbecausetheirmagneticfieldsaremisaligned.

D.Theyareararekindofneutronstarthatrotatefasterthannormal.

第12题

SelecttheTWOanswerchoicesfromparagraph5thatidentifywhyastronomershavedifficulty

findingpulsars.Toreceivecredit,youmustselectTWOanswers.

A.TheyarehiddenbehindlargerstarssocannotbeseenfromtheEarth.

B.Theslownessoftheirrotationmakesthemhardtoidentify.

C.TheirmagneticfieldsdonotlineupproperlywiththeEarth.

D.TheypulseontheX-rayband,whichmakesthemdifficulttosee.

第13题

Astarmustreachacertainsize—roughlyfourtoeighttimesthesizeofthesun—tobeableto

formaneutronstar.Starssmallerthanthattypicallybecomewhitedwarfswhentheycollapse

whilethoselargerthanthatnormallytransformintoblackholesuponcollapsing.Theformation

ofaneutronstaroccurswhenasupernovadestroysastar'souterlayeryetleavesthedensecore

intact.Thecenterofthestarisusuallycomprisedofiron,butotherelementsmaybepresentin

smalleramounts.❶Withthestar'souterlayersgone,nuclearfusionisnolongerpossible,which

resultsingravityhavingnocounterbalancingoutwardforce.❷Therefore,gravityactsstrongly

onthecoreandmakesitextremelydense.❸Asthisdensitygrowsinstrength,theelectronsand

protonsinthecore'satomsareforcedtogethertoformacoreofneutronsandneutrinos.❹The

neutronstarformsastructurewithdifferentlayers,muchlikeotherbodiesintheuniverse.Ifthe

neutronstarisrelativelyyoung,itisstillveryhot,soitssurfacemaybemoreliquidthansolid

whileitsinnercoreismuchdenserandmoresolidified.

*Glossary

nuclearfusion:areactioninwhichthenucleioflightatomsunitetoformthenucleiofheavier

atoms

neutrino:amasslessornearlymasslesslepton,anelementarytypeofparticle

Lookatthefoursquares[•]thatindicatewherethefollowingsentencecouldbeaddedtothe

passage.

Thisisthereasonthatthestarhasgottenitsparticularname.

Wherewouldthesentencebestfit?

Clickonasquare[•]toaddthesentencetothepassage.

第14题

Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.

CompletethesummarybyselectingtheTHREEanswerchoicesthatexpressthemostimportant

ideasofthepassage.Somesentencesdonotbelongbecausetheyexpressideasthatarenot

presentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.

Dragyouranswerchoicestothespaceswheretheybelong.Toremoveananswerchoice,clickon

it.Toreviewthepassage,clickonVIEWTEXT.

Whileneutronstarsaresmall,theyarebothverydenseandhot,andtheyblinkonaccountof

theirrapidspinning.

图片-ANSWERCHOICES

@Onlystarsofaparticularsizewilleverbecomeneutronstarswhentheirlivescometoanend.

©Astronomershaveonlyidentifiedaround2,000neutronstarsbecauseofthedifficultyinvolved

infindingthem.

③AneutronstarformswhenastarlargerthantheEarth'ssunbecomesasupernovabutkeeps

itscoreintact.

④Someneutronstarsspinveryquickly,andtheresultantblinkingcanbeseenfromtheEarthat

times.

©Neutronstarshaveonlybeenknownaboutsince1967,whenanastronomerfirstnoticedone

ofthem.

@Theforceofgravitymakesneutronstarsquitedense,andtheirtemperatureremainsveryhigh

overthecourseoftheirlives.下一题

（15~28/共54题）阅读理解

FACTORSTHATINFLUENCETIDES1Tidesareanaturalphenomenoninvolvingthe

alternatingriseandfallintheearth'slargebodiesofwatercausedbythegravitationalforcesof

themoonandthesun.Thecombinationofthesetwovariableforcesproducesthecomplex

recurrentcycleknownastheastronomicaltides.Tidesoccurinoceansandseas,toalimited

extentinlargelakesandtheatmosphere,and,toaveryminutedegree,intheearth'ssolidcrust.

2Theforcethatgeneratestidesistheinteractionoftwodifferentforces:thegravitational

attractionofthemoonactingupontheearth'swatersandthecentrifugalforceproducedbythe

revolutionoftheeartharoundthecenterofgravityoftheearth-moonsystem.Althoughthe

moonisonly384,395kilometersfromtheearth,comparedwiththesun'smuchgreaterdistance

of149,598,181kilometers,themoon'scloserdistanceoutranksitsmuchsmallermass,andthus

themoon'stide-raisingforceistwicemorethanthatofthesun.

3Thetide-generatingforcesofthemoonandsuncauseamaximumaccumulationofthe

oceanwatersattwooppositepositionsontheearth'ssurface.Thismeansthatatanygiventime

therearetwohightidesontheplanet.Oneisthedirecttideonthesidefacingthemoon;the

otheristheindirecttideontheoppositeside.Atthesametimethesetwohightidesoccur,

compensatingamountsofwateraredrawnfromallpointsthatare90degreesawayfromthese

bulges.Astheearthrotates,asequenceoftwohightidesandtwolowtidesisproducedeachday.

Successivehightidesoccurabout12.4hoursapart.Thedirecthightideatanygivenlocation

occurswhenthemoonisoverhead;lowtideoccurswhenthemoonisateitherhorizon.

4Thehighestandlowestlevelsofhightide,calledspringtideandneaptide,eachoccurs

twiceineverylunarmonthofabout27.5days.Aspringtideoccursatthenewmoonandatthe

fullmoon,whenthemoonandeartharealignedwiththesun,andthusthemoon'spullis

reinforcedbythesun'spull.Atspringtide,thedifferencebetweenhighandlowtidesisthe

greatest.Aneaptide,thelowestlevelofhightide,occurswhenthesun-to-earthdirectionisat

rightanglestothemoon-to-earthdirection.Whenthishappens,thegravitationalforcesofthe

moonandsuncounteracteachother;thus,themoon'spullisatminimumstrength,andthe

differencebetweenhighandlowtidesistheleast.Springandneaptidesatanygivenlocation

havearangeofabout20percentmoreorless,respectively,thantheaveragehightide.

5Theverticalrangeoftides—thedifferencebetweenhighandlow-variesaccordingtothe

size,surfaceshape,andbottomtopographyofthebasininwhichtidalmovementoccurs.

Typically,thetidalrangeintheopenoceanislessthanitisnearthecoasts.Forexample,inthe

openwaterofthecentralPacific,therangeisnomorethan0.3meters,butintherelativelysmall,

shallowNorthSea,itisabout3.6meters.AlongthenarrowchanneloftheBayofFundyinNova

Scotia,thedifferencebetweenhighandlowtidesmayreach16metersunderspringtide

conditions-theworld'swidesttidalrange.AtNewOrleans,whichisatthemouthofthe

MississippiRiver,theperiodicriseandfallofthetidesvarieswiththeriver'sstage,beingabout

0.24metersatlowstageandzeroathighstage.Ineverycase,actualhighorlowtidecanvary

considerablyfromtheaverage.

6Severalphysicalfactorsinfluencetidalranges,suchasabruptchangesinatmospheric

pressure,prolongedperiodsofextremehighorlowpressure,thedensityandvolumeofseawater;

andvariationsinocean-currentvelocities.Anyofthesefactorsalonecanaltersealevel;however,

incombinationwithearthquakes,hurricanes,orotherphenomena,theyareparticularlyforceful.

Hurricanewinds,forinstance,canheapoceanwaterintopowerfulstormsurgesthatincreasethe

impactoftheastronomicaltides.Whenastormsurgecoincideswiththeastronomicalhightide,

theresultingstormtidemayreachuptosixmetersormoreabovethenormalhightide.The

greaterandmorerapidthechangeofwaterlevel,thegreatertheerosiveeffectofthetidal

action.Currentscreatedbystormtidescombinewiththewavestoerodebeaches,coastal

highways,andfoundationsofbuildings.

第15题

Thewordrecurrentinparagraph1isclosestinmeaningto

A.repeating

B.mysterious

C.simultaneous

0.interrupted

第16题

Theforcethatcontrolstidesontheearthis

A.thegravitationalpulloftheplanet'score

B.thesameforcethatgeneratestidesonthemoon

C.abruptchangesinatmosphericpressure

D.acombinationofgravityandcentrifugalforce

第17题

Accordingtothepassage,themoon

A.hasagreaterdensitythanthesun

B.isclosertothesunthantheearthis

C.exertsagravitationalpullonthesun

D.affectstidesmorethanthesundoes

第18题

Thewordbulgesinparagraph3isclosestinmeaningto

A.currents

B.intervals

C.increases

D.waves

第19题

Whatcanbeinferredfromparagraph3?

A.Thedirecthightideishigherthantheindirecthightide.

B.Whenitishightideinsomeplaces,itislowtideinotherplaces.

C.Whenthemoonisdirectlyoverhead,thewaterisatitslowestlevel.

D.Atanygivenlocation,lowtideoccursabout12hoursafterhightide.

第20题

Aspringtideoccursatthetimeofthelunarmonthwhen

A.themoon'sgravitationalpullisatitsstrongest

B.themoonappearsasacrescentorhalf-circle

C.thesundoesnotexertanygravitationalforce

D.theverticalrangeofthetidesisverynarrow

第21题

Thewordcounteractinparagraph4isclosestinmeaningto

A.enhance

B.signal

C.oppose

D.avoid

第22题

Whichsentencebelowbestexpressestheessentialinformationinthehighlightedsentencein

paragraph4?Incorrectchoiceschangethemeaninginimportantwaysorleaveoutessential

information.

A.Thespringtideanywhereisaround20percenthigherthanthenormalhightide;theneaptide

is20percentlower.

B.lnsomeplaces,therehasbeena20percentchangeinthenumberofspringtidesandneap

tides.

C.lfthelocationofaspringtideisknown,thenaneaptideinthesamelocationwillbe20

percentless.

D.Thespringtideinonelocationisalways20higherthantheneaptideinanotherlocation.

第23题

TheauthormentionstheBayofFundyinparagraph5inorderto

A.comparetheBayofFundywithlargerbodiesofwater

B.explainwhyanarrowchannelisdangerousforships

C.givethemostextremeexampleofatidalrange

D.showhowriverscanaffecttheriseandfalloftides

第24题

Thewordprolongedinparagraph6isclosestinmeaningto

A.extended

B.surprising

C.predicted

0.dangerous

第25题

AllofthefollowingarementionedasinfluencesontheverticalrangeoftidesEXCEPT

A.thesizeandshapeofthewatersurface

B.suddenchangesinatmosphericpressure

C.risinglevelsofoceanwaterpollution

□.abnormalwaterlevelsduetostorms

第26题

Inparagraph6theauthormakesthepointthat

A.springtidesandstormsurgesareinterrelated

B.stormsenhancetheheightandstrengthoftides

C.oceancurrentsrarelychangeinspeedordirection

D.thegreatestimpactontidesisglobalwarming

第27题

Lookatthefoursquares,A,B,C,andD,whichindicatewherethefollowingsentencecouldbe

addedtothepassage.Wherewouldthesentencebestfit?

Thisabnormalriseinwaterlevelcancauseextremefloodinganderosionincoastalareas.

Severalphysicalfactorsinfluencetidalranges,suchasabruptchangesinatmosphericpressure,

prolongedperiodsofextremehighorlowpressure,thedensityandvolumeofseawater,and

variationsinocean-currentvelocities.AAnyofthesefactorsalonecanaltersealevel;however,in

combinationwithearthquakes,hurricanes,orotherphenomena,theyareparticularlyforceful.B

Hurricanewinds,forinstance,canheapoceanwaterintopowerfulstormsurgesthatincreasethe

impactoftheastronomicaltides.CWhenastormsurgecoincideswiththeastronomicalhightide,

theresultingstormtidemayreachuptosixmetersormoreabovethenormalhightide.DThe

greaterandmorerapidthechangeofwaterlevel,thegreatertheerosiveeffectofthetidal

action.Currentscreatedbystormtidescombinewiththewavestoerodebeaches,coastal

highways,andfoundationsofbuildings.

第28题

Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.Completethe

summarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthe

passage.Somesentencesdonotbelonginthesummarybecausetheyexpressideasthatarenot

presentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.

Manyfactorsinfluencetides,thealternatingriseand

fallintheearth'slargebodiesofwater.

AnswerChoices

A.Tidesoccurintheearth*satmosphereandwithintheearthitself.

B.Humanshavealwaysbeeninterestedinthemoon'sinfluenceontides.

C.Thecombinedgravitationalforcesofthemoonandthesunproducethecycleoftides.

D.Thelevelofthehightidevariesthroughoutthelunarmonth.

E.ThestageoftheMississippiRiverdeterminestheleveloftidesatNewOrleans.

F.Thecharacterofthebasinandvariousphysicalphenomenaaffecttheverticalrangeoftides.

上一题下一题

（29~40/共54题）阅读理解

POLITICALSYSTEMSOFTHETWENTIETHCENTURY1Monarchyisaformofgovernmentin

whichauthorityisheldbyasingleperson,amonarch,whosefighttoruleisgenerallyhereditary

andlifelong.Atthestartofthetwentiethcentury,monarchsruledovermostoftheworld,butby

themiddleofthecentury,onlyahandfulremained.Aseriesofrevolutionsinthepreceding

centurieshadweakenedtheEuropeanmonarchies,andwhilemonarchsremainedsymbolsof

nationalunity,realpowerhadpassedtoconstitutionalassemblies.Monarchysurvivedasaform

inEuropeonlywherethekingorqueenfunctionedasthesymbolicheadofaparliamentarystate,

asinBritain,theLowCountries,andScandinavia.ItlastedlongerinthefewsmallstatesofAsia

andAfricathathadnevercomeunderdirectcolonialrule.Bythe1960szautocraticmonarchyhad

becomeanoutdatedformofgovernment.Throughoutmostoftheworld,peoplewere

consideredcitizens,notsubjects,andthetotalityofthepeoplewereseenasconstitutingthe

state.

2Inmoststateswheremonarchicalauthoritywasremoved,someformofliberaldemocracy

tookitsplace.Aliberaldemocracyisastatewherepoliticalauthorityrestsinthepeopleacting

throughelectedrepresentativesandwhereanelectedexecutiveisresponsibletothewillofthe

peopleasawhole.Thetermappliestoabroadgroupofstateswithaparliamentaryor

representativepoliticaltradition.Liberaldemocraciesdifferfromthecommuniststatesknownas

people'sdemocracies,inwhichtheCommunistpartyholdstheultimateauthority.Generally,

liberaldemocraciesfollowtheparliamentarypattern,withtheexecutivepowervestedina

cabinetresponsibletotheparliamentanddrawnfromthemajoritypartyorcombinationof

parties.IntheUnitedStates,anindependentlyelectedexecutive,thepresident,functions

separatelyfromthelegislativeauthority,thecongress.

3Thedoctrinethatallofthepeoplehadeffectiveauthority,orsovereignty,becamethebasis

forthefunctioningofdemocraticstates.Thisdoctrineofpopularsovereigntybecame

all-inclusiveascitizenshiprightswereextendedtoclassesformerlyexcludedandtow