2023年吉大考博英語(yǔ)真題

PartIVocabularyandStructure(30%)

Directions:Thereare30incompletesentencesinthispart.Foreachsentencetherearefour

choicesmarkedA,B,CandD.ChoosetheONEthatbestcompletesthesentence.Thenmarkthe

correspondingletterontheANSWERSHEETwithasinglelinethroughthecenter.

1.Language,culture,andpersonalitymaybeconsideredofeachotherinthought,but

theyareinseparableinfact.

A.indistinctlyB.separatelyC.inelevantlyD.independently

2.Theworkwasdoneintheofreformsintheeconomic,socialandculturalspheres.

A.contextB.contestC.pretextD.texture

3.Thedeantriedtoretaincontrolofthesituationoncampus,buthisattemptwasbytheboardoftrustees.

A.approvedB.frustratedC.disclosedD.justified

4.Somejournalistsarefoundofoverstatingthesituationsothattheirnewsmaycreatea

great.

A.explosionB.sensationC.exaggeratingD.stimulation

5.Therewaslittle,ifany,evidencetosubstantiatethegossipand,therewaslittleto

disproveit.

A.bythesametokenB.underthesamecondition

C.atthesamestageD.forthesamepurpose

6.Everychemicalchangeeitherresultsfromenergybeingusedtoproducethechange,orcauses

energytobeinsomeform.

A.givenoffB.putoutC.setoffD.usedup

7.TheUnitedNationLawoftheSeaConferencewouldsoonproduceanocean-miningtreaty

followingitsdeclarationin1970thatoceansweretheheritageofmankind.

A.unanimousB.abstractC.autonomousD.almighty

8.Thisgrowthintheofdiabetesisdue,inpart,toanincreaseinobesity.

A.inferenceB.incidenceC.regulationD.repetition

9.Preliminaryestimationputsthefigureataround＄110billion,the＄160billionthe

PresidentisstrugglingtogetthroughtheCongress.

A.inproportiontoB.inreplytoC.inrelationtoD.incontrastto

10.France’sofnucleartestingintheSouthPaciticlastmonthtriggeredpolltical

debatesandmassdemonstrations.

A.assumptionB.consumptionC.presumptionD.resumption

11.Theofaoulturalphenomenonisusuallyalogicalconsequenceofsomephysical

aspectinthelifestyleofthepeople.

A.implementationB.demonstcationC.manifestationD.expedition

12.Readingthemindonlywithmaterialsofknowledge,itisthinkingthatmakeswhat

wereadour.

A.rectitiesB.prolongsC.minimizesD.furnishes

13.Previousstudiesprovokedbecausetheusedpatientswhosediagnosiswas

questionable.

A.contrlbutionB.contractionC.controversyD.convergence

14.Althoughthemodellooksgoodonthesurface,itwillnotbearclose.

A.temperamentB.contaminationC.scrutinyD.symmetry

15.IneversaidanythinglikethatatallYouarepurposelymyideastoproveyour

points.

A.revisingB.contradictingC.distortingD.distracting

16.Tosurviveintheintensetradecompetitionbetweencountries,companiesmustthe

qualitiesandvarietiesoftheirproductstotheworld-marketdemand.

A.forfeitB.enhanceC.guaranteeD.gear

17.Iwasunawareofthecriticalpointsinvoived,somychoicewasquite.

A.arbitraryB.rationalC.mechanicalD.unpredictable

18.Animportantpropertyofascientifictheoryisitsabilitytofurtherresearchand

furtherthinkingaboutaparticulartopic.

A.stimulateB.renovateC.arouseD.advocate

19.Alltheoff-shoreoilexplorerswereinhighspiritsastheyreadlettersfromtheir

families.

A.affectionateB.sentimentalC.intimateD.sensitive

20.Whoeverformulatedthetheoryoftheoriginoftheuniverse,itisjustandneedsproving.

A.spontaneousB.hypotheticalC.intuitiveD.empirical

21.Theceremonywillassoonasthepresidentarrives.

A.commendB.complyC.confrontD.commence

22.Thebarbarousaggressorsgrewmoreandmoreinslaughteringpeopleandburning

downtheirhouses.

A.amorphousB.ferociousC.audaciousD.egregious

23.SomeofthewordsemployedbyShakespeareinhisworkshavebecomeandareno

longerusedinthepresentdays.

A.obsoleteB.obsceneC.obviousD.oblique

24.Becauseoftheeconomicslowdown,thegovernmentchangeditspolicytorevenue

bylimitingcommerce.

A.disregardB.challengeC.diminishD.reject

25.Thespectatorsinthestadiumcheeredupwhentheysawhundredsofcolorfulballoons

slowlyintothesky.

A.descendingB.ascendingC.escalatingD.elevating

26.Anincreasingproportionofourpopulation,unabletolivewithoutadvanced

medical,willbecomeprogressivelymorereliantonexpensivetechnology.

A.interferenceB.interruptionC.interventionD.interaction

27.Severalintemationaleventsintheearly1990sseemlikelyto,oratleastweaken,

thetrendsthatemergedinthe1980s.

A.revoltB.revolveC.reverseD.revive

28.ForeigndisinvestmentsandtheofSouthAfricafromworldcapitalmarketsafter

1985furtherweakeneditseconomy.

A.displacementB.eliminationC.exclusionD.exception

29.Wearemovingtowardsamoreandcooperativesociety,whichisgettingbetterandbetter.

AfraternalBemotionalCexclusionDillegal

30.Thestudentwereaboutwhotheirnewteacherwouldbewhenthe

bellrangfortheirfirstclassinthenewsemester.

A.foreseeingB.speculatingC.fabricatingD.pondering

PartIIIReadingComprehension(60%)

Questions51to55arebasedonthefollowingpassage.

Whenadiseaseofepidemicproportionsripsintothepopulace,scientistsimmediatelygettowork,tryingtolocatethesourceoftheafflictionandfindwaystocombatit.Oftentimes,successisachieved,asmedicalscienceisabletoisolatetheparasite,germorcellthatcausestheproblemandfindswaystoeffectivelykillorcontainit.Inthemostseriousofcases,inwhichtheentirepopulationofaregionorcountrymaybeatgraverisk,itisdeemednecessarytoprotecttheentirepopulationthroughvaccination,soastosafeguardlivesandensurethatthediseasewillnotspread.

Theprocessofvaccinationallowsthepatient’sbodytodevelopimmunitytothevirusordiseasesothat,ifitisencountered,onecanfightitoffnaturally.Toaccomplishthis,asmallweakordeadstrainofthediseaseisactuallyinjectedintothepatientinacontrolledenvironment,sothathisbody’simmunesystemcanlearntofighttheinvaderproperly.Informationonhowtopenetratethedisease’sdefensesistransmittedtoallelementsofthepatient’simmunesysteminaprocessthatoccursnaturally,inwhichgeneticinformationispassedfromcelltocell.Thismakessurethat,shouldthepatientlatercomeintocontactwiththerealproblem,hisbodyiswellequippedandtrainedtodealwithit,havingalreadydonesobefore.

Therearedangersinherentintheprocess,however.Onoccasion,eventheweakenedversionofthediseasecontainedinthevaccineprovestoomuchforthebodytohandle,resultingintheimmunecaseofthesmallpoxvaccine,designedtoeradicatethesmallpoxepidemicthatnearlywipedouttheentireNativeAmericanpopulationandkilledmassivenumbersofsettlers.Approximately1in10,000peoplewhoreceivesthevaccinecontractthesmallpoxdiseasefromthevaccineitselfanddiesfromit.Thus,iftheentirepopulationoftheUnitedStatesweretoreceivetheSmallpoxVaccinetoday,3000Americanswouldbeleftdead.

Fortunately,thesmallpoxviruswasconsiderederadicatedintheearly1970s,endingthemandatoryvaccinationofallbabiesinAmericaIntheeventofare-introductionofthedisease,however,mandatoryvaccinationsmayresume,resultinginmoreunexpecteddeathsfromvaccination.Theprocess,whichistrulyablessing,mayindeedhidesomehiddencures.

51.Howdovaccinesprotecthumansfromdiseasesaccordingtoparagraphtwo?

A.Bypassinginformationonhowtofightthediseasetothedisease.

B.Bypassinginformationonhowtofightthediseasetotheimmunesystem.

C.Byweakeningthediseasesothattheimmunesystemcandefeatit.

D.Introducingthediseasetothebody,sothatsurvivorshavealreadyfoughtit.

52.Whatdoestheexampleofthesmallpoxvaccineillustrate?

A.Thewaythatvaccinesprotectpeoplefromdiseases.

B.Theeffectivenessofvaccinesineradicatingcertaindiseases.

C.Thepracticaluseofavaccinetocontrolanepidemicdisease.

D.Thepossiblenegativeoutcomeofadministeringvaccines.

53.Theauthorarguesthatvaccinationsarebothablessingandacursebecause.

A.savingthemanywouldnotnecessarilyjustifythedeathofthefew.

B.somevaccines,suchasthesmallpoxvaccine,havenegativesideeffects.

C.theydon’talwayswork.

D.whilemanylivesaresaved,SOMEAREACTUALLYKILLEDBYTHEVACCINT.

54.Thebesttitleforthepassagewouldbe.

A.“TheSmallpoxVaccine:AnAnalysis”.

B.“HowVaccinesWork”.

C.“Vaccines:MethodsandImplications”.

D.“AWarningontheNegativeSideEffectsofVaccines”.

55.Themainpurposeofthepassageisto.

A.convincethereaderthatvaccinesarenotassafeasmanythink.

B.educatethereaderonhowvaccinesareusedandsomeoftheirdangers.

C.educatethereaderonthecircumstancesthatwouldnecessitatewidespreadvaccinations.

D.presentthemethodbywhichvaccinesareusedthroughthecaseofthesmallpoxvaccine.

PassageTwo

Questions56to60arebasedonthefollowingpassage.

Fewnaturaldangersaremorefearedthanavalanches.AvalanchesareafamiliarpartofEuropeanhistory,ParticularlyintheSwissandFrenchAlps.Thisiswherethedirectionofwarshasturnedalmostinstantlybecauseofavalancheswipingoutinvadingarmies.

InNorthAmerica,avalanchesarelimitedalmostentirelytotheRockyMountainsandthelowerrangestothewest,theSierraNevadasandtheCascades.AvalancheshaveoccurredinthemountainsofNewEnglandbutnotwiththeregularityandintensityseeninthewesternmountains.

Severalmethodsareusedinexplainingandpredictingavalanches.Scientistsandlearningaboutthemusingresearchmethods.Somanyofthefactorsthatcreateavalanchesarehiddenbeneaththesnow’ssurfacethatpredictionsarestilllargelyguesswork.Therefore,wintertravelersmustassumetheworstofconditionswhenthetraversetheslopes.

Anavalancheoccurswhenagivenamountofsnowbecomestooheavyforwhateverisholdingitinplace.Itthenbreakslooseandslidesdownhill.

Avalanchesaredividedintotwogeneralcategories,loosesnowandslab.Aloosesnowavalancheusuallystartsatasinglepoint,suchasaskier’strack,andspreadsoutlikeafanorapyramidinachainreaction.Onecrystalbreaksanotherfree,whichmultiplesastheloosesnowmovesdownhill.Sometimestheseavalanchesstopafteronlyafewfeet.Sometimestheymovethousandsoftonsofsnowdownhillinspeedsupto300milesperhour.Thiscreatesashockwavethatcanflattenpartsofaforestthatarenoteventouchedbytheactualavalanche.

Slabavalanchesarethosethathaveawideareaofsnowwhichbreakslooseinalargepiece.Thesecanrangeinsizefromjustafewsquarefeeltothousandsofsquarefeetofsnow.Themostdangerousandcommontypeofavalancheforskiersistheso-called“softslab”avalanche.Thistypeoccursmostoftenduring,orjustafteraheavysnowfall.Thesnowhasn’tyethadachancetosettleandadheretothetemperature,thelesslikelythenewsnowwillformabondwiththe

existingsnow.

56.Whatwouldbethebesttitleforthispassage?

A.Avalanches

B.TheHistoryofAvalanches

C.SkiersBeware

D.AvalanchesCanKill

57.Accordingtothepassage,howdidavalanchesaffectwars?

A.Theyhidthearmiesapproachingthecityaidingintheattack.

B.Theykilledthearmiesapproachingthecity.

C.Theyblockedpathsintothecity.

D.Theysnowblindedtheapproachingarmies.

58.Accordingtothepassage,whatmustskiersassumeaboutavalancheswhenskiing?

A.Theyonlyhavetoworryafteraheavysnowfall.

B.AvalanchesonlyoccurintheSwissorFrenchAlps.

C.Theyshouldalwaysexpectthatanavalanchewilloccur.

D.WhenskiinginNewEngland,theywillneverhavetoworryaboutanavalanche.

59.Accordingtothepassage,whenisthemostdangeroustimeforskiers?

A.Whenthetemperatureisbelow20degreesF.

B.Rightbeforeasnowstorm.

C.Duringasnowstorm.

D.Inthewinter.

60.Accordingtothepassage,whichfactorcausesanavalanche?

A.Theslopeofthemountain.

B.Thesizeofthesnowfall.

C.Theamountandintensityofmovementaroundthesnowfall.

D.Theweightofthesnow.

PassageThree

Questions61to65arebasedonthefollowingpassage.

Recentstoriesinthenewspapersandmagazinessuggestthatteachingandresearchcontradicteachother,thatresearchplaystooprominentapartinacademicpromotions,andthatteachingisbadlyunderemphasized.Thereisanelementoftruthinthesestatements,buttheyalsoignoredeeperandmoreimportantrelationships.

Researchexperienceisanessentialelementofhiringandpromotionataresearchuniversitybecauseitistheemphasisonresearchthatdistinguishessuchauniversityfromanartscollege.Someprofessors,however,neglectteachingforresearchandthatpresentssproblem.

Mostresearchuniversitiesrewardoutstandingteaching,butthegreatestrecognitionisusuallygivenforachievementsinresearch.Partofthereasonisthedifficultyofjudgingteaching.Ahighlyresponsibleandtoughprofessorisusuallyappreciatedbytopstudentswhowanttobechallengedbutdislikedbythosewhoserecordsarelessimpressive.Themildprofessorgetsoverallratingsthatareusuallyhigh,butthereisasenseofdisappointmentonthepartofthebeststudents,exactlythoseforwhomthesystemshouldpresentthegreatestchallenges.Thus,auniversitytryingtopromoteprofessorsprimarilyonthebasisofteachingqualitieswouldhavetoconfrontthisconfusion.

Asmodernsciencemovesfaster,twoforcesareexertedonprofessors:oneisthetimeneededtokeepupwiththeprofession;theotheristhetimeneededtoteach.Thetrainingofnewscientistsrequiresoutstandingteachingattheresearchuniversityaswellastheartscollege.Althoughscientistsareusually“made”intheelementaryschools,scientistscanbe“l(fā)ost”bypoorteachingatthecollegeandgraduateschoollevels.Thesolutionisnottoseparateteachingandresearchbuttorecognizethatthecombinationisdifficultbutvital.Thetitleofprofessorshouldbegivenonlytothosewhoprofessanditisperhapstimeforuniversitiestoreserveitforthosewhoprofessanditisperhapstimeforuniversitiestoreserveitforthosewillingtobeanearnestpartofthecommunityofscholars.Professorsunwillingtoteachcanbecalled“distinguishedresearchinvestigators”ofsomethingelse.

Thepaceofmodernsciencemakesitincreasinglydifficulttobeagreatresearcherandagreatteacher.Yetmanyaredescribedinjustthoseterms.Thosewhosaywecanseparateteachingandresearchsimplydonotunderstandthesystem,butthosewhosaytheproblemwilldisappeararenotfulfillingtheirresponsibilities.

61.Whatideadoestheauthorwanttoconveyinthefirstparagraph?

A.Therelationshipbetweenteachingandresearchshouldnotbesimplified.

B.Teachingandresearcharecontradictory.

C.Researchcanneverbeemphasizedtoomuch.

D.Itiswrongtooverestimatetheimportanceofteaching.

62.Inacademicpromotionsresearchuniversitiesstillattachmoreimportancetoresearchpartly

because.

A.researchimprovesthequalityofteaching.

B.studentswhowanttobechallengedappreciateresearchprofessors.

C.professorswithachievementsinresearchareusuallyresponsibleandtough.

D.itisdifficulttoevaluateteachingqualityobjectively.

63.Accordingtothefourthparagraph,whichofthefollowingwilltheauthorprobablyagreewith?

A.Distinguishedprofessorsatresearchuniversitiesshouldconcentrateonresearchonly.

B.Itisofutmostimportancetoimproveteachinginelementaryschoolsinordertotrainnew

scientists.

C.Theseparationofteachingfromresearchcanlowerthequalityoffuturescientists.

D.Therapiddevelopmentofmodernsciencemakesitimpossibletocombineteachingwith

research.

64.Thetitleofprofessorshouldbegivenonlytothosewhofirstandforemostdo.

A.scientificresearch

B.teaching

C.fieldwork

D.investigation

65.Thephrase“theproblem”(Line4,Para.5)refersto.

A.raisingthestatusofteaching.

B.theseparationofteachingfromresearch.

C.thecombinationofteachingwithresearch.

D.improvingthestatusofresearch..

PassageFour

Questions66to70arebasedonthefollowingpassage.

Largecompaniesneedawaytoreachthesavingsofthepublicatlarge.Thesameproblem,onasmallerscale,facespracticallyeverycompanytryingtodevelopnewproductsandcreatenewjobs.Therecanbelittleprospectofraisingthesortofsumsneededfromfriendsandpeopleweknow,andwhilebanksmayagreetoprovideshort-termfinance,theyaregenerallyunwillingtoprovidemoneyonapermanentbasisforlong-termprojects.Socompaniesturntothepublic,invitingpeopletolendthemmoney,ortakeashareinthebusinessinexchangeforashareinfutureprofits.ThistheydobyissuingstocksandsharesinthebusinessthroughTheStockExchange.Bydoingso,theycanputintocirculationthesavingsofindividualsandinstitutions,bothathomeandoverseas.

Whenthesaverneedshismoneyback,hedoesnothavetogotothecompanywithwhomheoriginallyplacedit.Instead,hesellshissharesthroughastockbrokertosomeothersaverwhoisseekingtoinvesthismoney.

ManyoftheservicesneededbothbyindustryandbyeachofusareprovidedbytheGovernmentorbylocalauthorities.Withouthospitals,roads,electricity,telephones,railways,thiscountrycouldnotfunction.Alltheserequirecontinuousspendingonnewequipmentandnewdevelopmentiftheyaretoserveusproperly,requiringmoremoneythanisraisedthroughtaxesalone.TheGovernment,localauthorities,andnationalizedindustriesthereforefrequentlyneededtoborrowmoneytofinancemajorcapitalspending,andthey,too,cometoTheStockExchange.

Thereishardlyamanorwomaninthiscountrywhosejoborwhosestandardoflivingdoesnotdependontheabilityofhisorheremployerstoraisemoneytofinancenewdevelopment.Inonewayoranother,thisnewmoneymustcomefromthesavingsofthecountry.TheStockExchangeexiststoprovideachannelthroughwhichthesesavingscanreachthosewhoneedfinance.

66.Almostallcompaniesinvolvedinnewproductionanddevelopmentmust.

A.relyontheirfinancialresources.

B.persuadethebankstoprovidelong-termfinance.

C.borrowlargesumsofmoneyfromfriendsandpeopleweknow.

D.dependonthepopulationasawholeforfinance.

67.Themoneywhichenablesthesecompaniestogoaheadwiththeirprojectsis.

A.repaidtoitsoriginalownersassoonaspossible.

B.raisedbythesellingofsharesinthecompanies.

C.exchangesforpartownershipinTheStockExchange.

D.investedindifferentcompaniesonTheStockExchange.

68.Whenthesaverswanttheirmoneybackthey.

A.askanothercompanytoobtaintheirmoneyforthem.

B.lookforotherpeopletoborrowmoneyfrom.

C.puttheirsharesinthecompanybackonthemarket.

D.transfertheirmoneytoamoresuccessfulcompany.

69.Alltheessentialservicesonwhichwedependare.

A.runbytheGovernmentorourlocalauthorities.

B.inconstantneedoffinancialsupport.

C.financedwhollybyratesandtaxes.

D.unabletoprovidefortheneedsofthepopulation.

70.TheStockExchangemakesitpossiblefortheGovernment,localauthoritiesandnationalized

industries.

A.toborrowasmuchmoneyastheywish.

B.tomakecertaineverybodysavesmoney.

C.toraisemoneytofinancenewdevelopments.

D.tomakecertaineverybodylendsmoneytothem.

PassageFive

Questions71to75arebasedonthefollowingpassage.

Theproducersofinstantcoffeefoundtheirproductstronglyresistedinthemarketplacesdespitetheirmanifestadvantages.Furthermore,theadvertisingexpenditureforinstantcoffeewasfargreaterthanthatforregularcoffee.Effortsweremadetofindthecauseoftheconsumers’seeminglyunreasonableresistancetotheproduct.Thereasongivenbymostpeoplewasdislikeforthetaste.Theproducerssuspectedthattheremightbedeeperreasons,however.Thiswasconfirmedbyoneofmotivationresearch’sclassicstudies,oneoftencitedinthetrade.MasonHaire,oftheUniversityofCalifornia,constructedtwoshoppingliststhatwereidenticalexceptforoneitem.Thereweresixitemscommontobothlists:hamburger,carrots,bakingpowder,bread,cannedpeachesandpotatoes,withthebrandsoramountsspecified.Theseventhitem,inthefifthplaceonbothlists,read“Ilb.MaxwellHousecoffee”ononelistand“Nescafeinstantcoffee”ontheother.Onelistwasgiventoeachpersoninagroupoffiftywomen,andtheotherlisttothoseinanothergroupofthesamesize.Thewomenwereaskedtostudytheirlistsandthentodescribe,asfarastheycould,thekindofwoman(“personalityandcharacter”)whowoulddrawupthatshoppinglist.Nearlyhalfofthosewhohadreceivedthelistincludinginstantcoffeedescribedahousewifewhowaslazyandapoorplanner.Ontheotherhand,onlyonewomanintheothergroupdescribedthehousewife,whohadincludedregularcoffeeonherlist,aslazy,onlysixofthatgroupsuggestedthatshewasapoorplanner.Eightwomenfeltthattheinstant-coffeeuserwasprobablynotagoodwife!Nooneintheothergroupdrewsuchaconclusionaboutthehousewifewhointendedtobuyregularcoffee.

71.Thefactthatproducersfoundresistancetotheirproductdespitethefactthattheyspentmoreadvertisingmoneyoninstantthanregularcoffeeshowsthat.

A.advertisingdoesnotassurefavorablesalesresults.

B.companiesspentmoremoneyonadvertisingthantheyshould.

C.peoplepaylittleattentiontoadvertising.

D.themoreoneadvertisesthebetterthesalespicture.

72.Inthisinstance,thepurposeofmotivationresearchwastodiscover.

A.whypeopledrinkcoffee.

B.whyinstantcoffeedidnottastegood.

C.whyregularcoffeewassuccessful.

D.therealreasonwhypeoplewouldnotbuyinstantcoffee.

73.Thisinvestigationindicatedthat.

A.50percentofhousewivesarelazy.

B.housewiveswhouseinstantcoffeearelazy.

C.manywomenbelievethatwiveswhouseinstantcoffeearelazy.

D.wiveswhouseregularcoffeearegoodplanners.

74.Ontheresultsofthistest,theproducersprobablyrevisedtheiradvertisingtoshowa.

A.lazyhousewifeusingregularcoffee.

B.hard-workinghousewifeusinginstantcoffee.

C.lazyhousewifeusinginstantcoffee.

D.manobviouslyenjoyingthetasteofinstantcoffee.

75.Impliedbutnotstated.

A.Despiteitsadvantages,mostpeopledislikedinstantcoffeebecauseofitstaste.

B.Theadvertisingexpenditureforinstantcoffeewasgreaterthanthatforregularcoffee.

C.Veryoftenwedonotknowtherealreasonsfordoingthings.

D.Tasteistheprincipalfactorindeterminingwhatwebuy.

PassageSix

Questions76to80arebasedonthefollowingpassage.

Inrecentyears,therehasbeenanincreasingawarenessoftheinadequaciesofthejudicialsystemintheUnitedStates.Costsarestaggeringbothforthetaxpayersandthelitigants—andthelitigants,ofparties,havetowaitsometimesmanyyearsbeforehavingtheirdayincourt.Manysuggestionshavebeenmadeconcerningmethodsofameliorating（改善）thesituation,butasinmostbranchesofgovernment,changescomeslowly.

Onesuggestionthathasbeenmadeinordertomaximizetheefficiencyofthesystemistoallowdistrictsthathaveanoverabundanceofpendingcasestoborrowjudgesfromotherdistrictsthatdonothavesuchabacklog.Anothersuggestion