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若x，y满足约束条件，则z＝x﹣2y的最大值为（ ）
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高三下学期数学《》真题及答案
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若变量xy满足约束条件则z=x﹣2y的最大值为
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3
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设变量xy满足约束条件则z=3x﹣2y的最大值为.
.若xy满足约束条件则z=x﹣2y的最大值为.
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若xy满足约束条件则z=x+y的最大值为_____________.
若xy满足约束条件则z=x+y的最大值为.
若xy满足约束条件则z=2x+y的最大值为.
若变量xy满足约束条件则z=x-2y的最大值为.
已知xy满足约束条件则z=x+2y的最大值为
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设变量xy满足约束条件则z=x﹣2y的最大值为
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若实数xy满足约束条件则z=|x+2y-4|的最大值为.
设xy满足约束条件则z=x﹣2y的最大值为.
已知变量xy满足约束条件若z=2x-y的最大值为2则实数m的值为.
设变量xy满足约束条件其中a>1若目标函数z＝x＋y的最大值为4则a的值为________.
若变量xy满足约束条件则z=2x+y的最大值为.
设变量xy满足约束条件则目标函数z＝4x＋2y的最大值为
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若xy满足约束条件则z=2x+y的最大值为.
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若实数xy满足约束条件则目标函数z=2x+3y的最大值为
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假设你应邀参加学校组织的英语学习师生座谈会请你根据下表所提示的信息用英语写一篇发言稿简单介绍自己英语学习的情况并对学校今后的英语教学提出建议. 注意 1对所给要点逐一陈述适当发挥不要简单翻译. 2词数150左右.开头和结尾已经写好不计人总词数. DearteacherandschoolmatesIt'sagreatpleasureformetobetodayandsharemyexperienceoflearningEnglishwithyou. Thankyouforlistening.
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Itimpressedmealot.Ineverthoughtthatlittlehelpwould1outtobethemostsatisfyingthingIhaveeverdone.Hewastiredand2toclimbfurther.Withabroad3heaskedifIcouldhelphimwithsomemoney.Hewasparalyzedinbothlegsandwas4fundsforsomeoperation.Hesaidthatifoperatedsuccessfullyhecould5trainingguaranteeinghimajob.Iwasfullof6andevenaskedhimtoshowhislegs.Igavehimthe7money.Afterafewdaysheagaincameatmydoorstepaskingformoremoneyforaccommodation.ThistimeIwasmoreorless8heisnotcheatingme.IgavehimsomeandsaidthisisallIhad. AyearwentbyandIhadmovedtoan9place.OnefinedayIgotacallfromanunknownnumber.ThecallercalledouthisnamebutIdidn't10him.ThenhesaidheistheveryparalyzedpersonIhelpedayearago. Iaskedhimhowheisdoing.HesaidWhatsir?yourecognizemenotbymynamebutbymy11state. WithyourkindhelpIamnowableto12onmylegswithoutsupport.Iwasoperated13.Iammarriedtoabeautifulladyandhaveastable14. Idon't15rememberifIgavehimmyphonenumber.16whathesaidnextwastouching.HesaidhewantedtoreturnmymoneysothatIdidn'tfeelcheatedandcontinuedtohelppeople17inthefuture.Idon'tknowwhetherhereadmyfacialexpressionthedayIhelpedhimbuttearswere18downmyface.ThatdayIpromisedhimIwillcontinuetohelppeopleasIseean19﹣smallorbig.20thatchangedmylife. 1A.send B.bring C.turn D.break 2A.playing B.substituting C.struggling D.walking 3A.look B.whisper C.view D.smile 4A.raising B.finding C.seeking D.earning 5A.pretend B.attend C.intend D.tend 6A.doubts B.minds C.worries D.depression 7A.remaining B.left C.hiding D.forgotten 8A.informed B.outspoken C.convinced D.prepared 9A.bad B.old C.systematic D.new 10A.remind B.recognize C.replace D.repeat 11A.disabled B.messed C.excited D.stressed 12A.live B.stand C.focus D.base 13A.surprisingly B.successfully C.hopefully D.naturally 14A.reason B.promise C.character D.job 15A.also B.even C.already D.only 16A.Therefore B.Otherwise C.However D.Meanwhile 17A.infavor B.inplace C.inadvance D.inneed 18A.running B.putting C.bringing D.pulling 19A.behavior B.case C.accident D.opportunity 20A.Strangely B.Truly C.Generally D.Originally
Nooneknowsexactlyhowtheearthbegan．AccordingtoawidelyacceptedtheorytheearthwasjustacloudofdustaftertheBigBang．Thenthedustsettledintoasolidglobewhichexplodedviolentlywithfireandrockandproducedwatervaporandmanygasesmakingtheearth'satmosphere．1Whatisevenmoreimportantisthatastheearthcooleddownwaterappearedandstayedonthesurface．Itwasthe2presencepresentofwaterthatallowedtheearthtodissolveharmfulgasesandacidsintotheoceansandseas．Thisproducedachainreaction3whichmadeitpossibleforlifetodevelop．Firsttheappearanceofsmallplantsencouragedthedevelopmentofearlyshellfishandallsortsoffish．Nextgreenplantsbegantogrowonland．They4werefollowedfollowbylandanimals．Somewereinsects．Otherscalledamphibians5werebeabletoliveonlandaswellasinthewater．Soreptilesappearedforthefirsttime．Theyproducedyounggenerallyby6layinglayeggs．Laterdinosaursdeveloped．7Unluckilylucktheysuddenlydisappeared．Afterthatmammalscameintobeingandexistedontheearth．Theseanimalsweredifferentfromalllifeformsinthepastbecausetheygavebirth8toyoungbabyanimalsandproducedmilktofeedthem．Finallyhumansbecomethemostimportantanimalsontheplanet．However9theyareputtingtoomuchcarbondioxideintotheatmospherewhichpreventsheat10escapingescapefromtheearthintospacemakingtheearthtoohottoliveon．Asaresultofthiswhetherlifewillcontinueontheearthwilldependonwhetherthisproblemcanbesolved．
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氮元素是植物生长的必需元素合理施用氮肥可提高农作物的产量．回答下列问题． 1植物细胞内在核糖体上合成的含氮有机物是在细胞核中合成的含氮有机物是叶绿体中含氮的光合色素是． 2农作物吸收氮元素的主要形式有铵态氮NH4+和硝态氮NO3﹣．已知作物甲对同一种营养液以硝酸铵为唯一氮源中NH4+和NO3﹣的吸收具有偏好性NH4+和NO3﹣同时存在时对一种离子的吸收量大于另一种．请设计实验对这种偏好性进行验证要求简要写出实验思路预期结果和结论．
ThePianoPracticePhysician'sHandbookbyColourfulKeys Price﹩7.99 Words25570 LanguageEnglish PublishedApril182017 CategoryNonfiction Rightnowallovertheworldpianostudentsarewastingtheirpreciouspracticetime.Thebooktakesafreshlookathowpianoteachersteachpracticeskills. TheSpearThrowerbyPamelaLoveridge Price﹩4.99 Words68860 LanguageEnglish PublishedOctober232017 CategoryFiction AbouteightythousandyearsagoineasternAfricaayoungnativenamedNibuwitnessessomelionskillhisparentswhileouthunting.ItisunexpectedthatevenaftersuchaterribleeventNibuisinspiredtoinventthethrowingspearaweaponthatisfarsuperiortotheoldhandspearandwhichwillchangeourhistoryforever. AllTheWayDownbyDavidKearns Price﹩3.99 Words57940 LanguageAmericanEnglish PublishedOctober252016 CategoryFiction BountyhunterDeloreanHarperinvestigateshisbrother'sdeathinaminingaccidentinAlamogordoNewMexico.Soonitbecomesclearthathisbrother'sdeathisnoaccidentandDeloreanhasbecomethenexttargetofakillerwhowilldoanythingtocoverhistracks.Willhebeabletouncoverthemysteryofhisbrother'sdeathorwillhebekilled? TheMakingofaWarriorbyWillEdwards PriceFree! Words5940 LanguageEnglish PublishedAugust192016 CategoryFiction Youmaybelookingforsuccessrightnow.Perhapsyouarestilllookingforthatwisdomthatcanmakethedifferenceandpushyouforwardtowardyourgoal.Wellyouwillfindsomethingofrealvalueinthislittlebookwhichwaswrittenespeciallyforyou. TheWorkExperiencebyLTait Price﹩2.30 Words34210 LanguageEnglish PublishedApril162017 CategoryNonfiction Itisahumorouslookatvariousaspectsofthemodernworkingworld!Itcoversaseriesofsubjectsfrommyexperiencesoftrulyhorriblebossestothepitfalls陷阱ofjobseekingandinterviewsalongwithsomeotherfunthings! 1Nibuisprobably. A.abraveAfricanchild B.acreativeyoungman C.aneducatedteenager D.anextremelypooradult 2WhatcanwelearnaboutDeloreanHarper? A.Heiskilledinhisbrother'smine. B.Hetrieshisbesttocoverhistracks. C.Heriskshislifetofindoutthetruth. D.Hisbrotherdiesinacaraccident. 3Thosewhosearchforsuccessmayturnto. A.TheSpearThrower B.AllTheWayDown C.TheWorkExperience D.TheMakingofaWarrior 4Whichofthefollowingisintendedtoentertainreaders? A.AllTheWayDown B.TheSpearThrower C.TheWorkExperience D.ThePianoPracticePhysician'sHandbook 5Amongthesefivebooks. A.onlyonebookisfree B.theyallbelongtofiction C.theywereallpublishedin2017 D.theyareallwritteninAmericanEnglish
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Asurveyhasshownthatwhatyoudoonaplanecanbedeterminedbywhichnationalityislistedonyourpassport． AccordingtotheresultsofaninternationalpassengersurveyAustraliansarethebiggestdrinkersonboardwith36percentchoosingtodownthehatchcomparedto35percentofAmericansand33percentofBrits． TheAirlinePassengerExperienceAssociationAPEXspoketoaround1500peopleaged18andolderwhohavetraveledbyplaneatleastonceduringthelastthreemonthsandwerelivingintheUnitedStatesUnitedKingdomGermanyJapanChinaSingaporeAustraliaorBrazil． TheresultsfoundChinesetravelersaremostlikelytonodoffoncetheseat﹣beltsignswitchesoff．Theyarealsothefirsttoreachfortheircreditcardforsomein﹣flightshoppingandthebiggestfansofgaming．Americansontheotherhandliketousetheirtimeintheairmoreproductively﹣﹣﹣whennotdrinking﹣﹣﹣choosingtoworkwhileflyingat35000feet． MeanwhileBritsandGermansarethebestatmakingchatwithrandomstrangers﹣﹣﹣spending50percentmoretimethananyothernationality．ComparativelyBraziliansconducttheirconversationsonlineviaemailmessagingappsorsocialmedia． Despiteplanefoodhavingabadreputationsevenoutoftenintervieweessaidtheywerehappytoeatupontheselectionofin﹣flightsnacksandmeals．In﹣flightmagazineswerealsopopularwithfouroutoffivepassengersclaimingtoreadthem． Theinternationalflyersdidhoweverexpresstheirdesireforbetterin﹣flightentertainment．TheindustryhasgreatlyimprovedthecomfortentertainmentandonboardserviceandpassengersareacceptingthoseimprovementssaidRussellLemieux．APEXexecutivedirector．Atthesametimepassengersaredemandingmorefromtheirairtravelexperienceswhichwilldrivemoreimprovementstouchingallaspectsofthejourneyheadded． 1WhatcanyouprobablyseeintheflightaccordingtothepassageB A．Brazilianschoosetodrink． B．Germanschattokilltheirtime． C．Americansdoin﹣flightshopping． D．TheChineseswitchofftheseat﹣beltsign． 2WhenonboardtheplaneA． A．mostpassengersliketoreadin﹣flightmagazines B．passengersfromonenationhavelittleincommon C．morethanhalfofthepassengersdon'tenjoyplanefood D．mostpeopletendtousein﹣flighttimetohaveagoodsleep 3WhatcanwelearnfromthelastparagraphD A．Flyerscarelittleaboutentertainment． B．Flyersareexpectingbetterflightexperiences． C．Flyersarenotsatisfiedwiththeimprovement． D．Flyershavemoreandmoredemandsfromairlines． 4What'sthepurposeofthepassageD A．Toentertainreaderswithinterestingstories． B．Toencouragepeopletobehavewellinpublic． C．Tocriticizeimpolitebehaviorsontheplane． D．Toinformreadersoftheresultsofasurvey．
用数学归纳法证明“1-+-+…+＝n∈N*”第一步应验证的等式是从“n＝k”到“n＝k+l”左边需增加的代数式是
Jennywasdrivinghersix﹣year﹣oldsonTonytohispianolesson.TheywerelateandJennywasbeginningtothinksheshouldhavegivenitup.TherewasalwayssomuchtodoandJennyrecentlyhelpedwithanoperation.Shewastired.Thestormandiceroadsaddedtohertension.Maybesheshouldturnthecararound. Mom!Tonycried.Look!Justaheadacarhadlostcontrolonthepatchofice.AsJennytappedthebrakestheothercarwildlyrolledoverthencrashedsidewaysintoatelephonepole. Jennypulledoverstoppedandthrewopenherdoor.Thankgoodnesssheknewherjobwell﹣shemightbeabletohelptheseunfortunatepassengers.Thenshepaused.WhataboutTony?Shecouldn'ttakehimwithher.Littleboysshouldn'tseesceneslikethat.Butwasitsafetoleavehimalone?Whatiftheircarwerehitfrombehind?ForabriefmomentJennyconsideredgoingonherway. SheaskedTonytostayinthecarandranslippingandslidingtowardthecrashsite.Itwasworsethanshe'sfeared.Twogirlsofhighschoolageinthecar.Onewaskilled.Thedriverhoweverwasstillbreathing.Jennyquicklyappliedpressuretothewoundintheteenager'sheadwhileherpracticedeyecheckedtheotherinjuries.Abrokenlegmaybetwoalongwithprobableinternalbleeding.Butifhelpcamesoonthegirlwouldlive. Atruckerhadpulledupandwascallingforhelponhiscellphone.Soonambulanceandrescueworkerscame.Goodjobonesaidwhileexaminingthewounds.Youprobablysavedherlife!LaterthefamiliesofthevictimscametomeetJennyexpressingtheirgratitudeforthehelpshehadoffered. 1WhatwasJennydoingwhentheaccidenthappened? A.Shewashelpingwithanoperation. B.Shewasdrivingforherson'slesson. C.Shewasdrivinghomewithherson. D.Shewasmakingatelephoneforhelp. 2WhatdoesJennydoaccordingtothepassage? A.Ataxi﹣driver. B.Afirefighter. C.Anurse. D.Ateacher. 3Thecaraccidentwascausedby. A.thetirednessofthedriver B.thetruckwhowastelephoningwhiledriving C.thestudents'carelessdriving D.thebadweatherandterribleroadconditions 4BeforegoingtorescuethewoundedJennyworriedalotabout. A.herpoorskillsofsavingpeople B.herlittleson'ssafetyinthecar C.herlittleson'spianolesson D.thestudentskilledintheaccident 5Wecaninferfromthepassagethat. A.thedriverwassavedthankstoJenny'stimelyhelp B.therewereatleasttwodeathsinthecaraccident C.Jennywastoblamefortheterriblecaraccident D.Jennywaslateforhispianolessonsforthisaccident
Growersaroundtheworldareusingnewmethodstogrowgrapestomakewine．Theyusenaturalandorganicmethodstocontrolharmfulinsectsandweedsinsteadofusingchemicals．NowawineryinCanadahasadoptedanaturalwaytocontrolitsgrapevines葡萄藤．TheFeatherstoneWineryisinsouthernOntario．Thegrapevineslikeotherplantsneedtobecuteveryyear． Cuttinggrapevinesmustbedoneverycarefully．Onlyatargetedareaofleavesisremovedfromthelowerpartofthevinestohelpthegrapesgrowbetter．ButattheFeatherstoneWinerynomanormachinedoesthecutting．Insteadthejobisdoneby40littlewoolylambs． DavidJohnsonownsthevineyard．HesayshelearnedaboutusinglambswhilevisitingwineriesinNewZealand．Theyounglambsareperfectlydesignedtodothejob．Theyeatthegrapeleavesonthelowerpartsofthevine．Buttheyarenottallenoughtoreachthegrapes．Theyonlyweighabout22kilogramssotheydonotbeatdownthesoil．Andtheirwastemakesgoodorganicfertilizer．Inadditionusingthelambscostsmuchlessthanhiringworkerstocutthevinesforsevenweeksinsummer．AndwhenthecuttingisdoneinAugustthelambsbecometastydishes． Mr．Johnsonsayshehadadifficulttimefindingenoughlambstodothejob．Thereareabout50millionlambsinNewZealand．ButtherearenotnearlyasmanyinOntario．Alsosomeorganicpesticides杀虫剂areharmfultolambs．Andthelambsmustbewatchedtomakesuretheydonoteattoomuchofthegrapevines． DavidJohnsonsaysthelambshelphimcarryouthisenvironmentalideasaboutfarming．Theyarelovelyandpeacefulandhelikeshavingtheminhisvineyard．Peoplevisitingthevineyardalsoenjoywatchingthelambsdotheirjob． 1InordertohelpthegrapesgrowbettergrowersB． A．onlyhavetoremovethedeadleaves B．needtoremoveaspecificareaofleaves C．shouldn'tremoveanypartoftheplants D．shouldletlittlelambsdothecutting 2WhichofthefollowingstatementsaboutusinglambstodothecuttingisnotrightA A．Usinglambscostsmorethanhiringworkers． B．Lambswon'teatthegrapes． C．DavidJohnsonlearnedthiswayinNewZealand． D．Lambscanbeeatenafterthecuttingisdone． 3Paragraph4ismainlyaboutD． A．thefutureofgettinglambstodothecutting B．theworriesaboutusingorganicpesticides C．thewaystogetlambstodothecutting D．theproblemsrelatedtolambsdoingthecutting 4WecaninferfromthepassagethatDavidJohnsonC． A．ownsseveralwineriesinCanada B．buyslambsfromNewZealand C．isconcernedaboutprotectingthecircumstance D．loveskeepinglambsinsteadoffarming
IwaswalkingonenightacrossasquareofCopenhagen．DenmarkwhenIwassuddenly1Abyasmallcrowdbythetownhall． Twopoliceofficersamanandawomanwerewalkingsoftlyandwith2Btoaboyofaboutseventeen．Obviouslydrunkhehad3Chisheadbloodranabovehishairlinetohischeek． Thiswasprobablythe4Bthingthetwopoliceofficerswouldhaveto5Aallevening．TheDanesarealaw﹣abiding守法的people．Themost6Dcrimeinthiscountryisbicycletheftbesidesmurders．ThereweresixmurdersinCopenhagentheyearbefore7D1688inNewYork．Thecityisso8CthatQueenMagaretheusedtovisitflowershopsjustlikeanordinary9A．IoncetalkedtoaDanewhohadguardedherinsuch10C．Whenaskedwhetherhe11DhersafetyhelookedatmesurprisedandrepliedWhyweallloveher12Bwasquitesweet． AsthepoliceofficersledtheboytotheircarwithgreatcareIfoundmyself13Atheminvoluntarily．Idon'tknowwhyIwassointerestedexceptthatIhadneverseensuch14Bpolice．IsaidtothewomanofficerExcusemewhatwillyoudowiththeboy We'lltakehimhomeshesaid15A． Iwas16C．Icouldn'thelpthinkingofthetimeIwasstoppedbypoliceinNewYorkand17Dtostandagainstawallandfrisked搜身becauseofanunpaidticket．Iwasaboutseventeenatthetime． Willhebein18CforthisIasked． Withhisfathermostprobably．Butnotwithus．Weareallalittle19Asometimesyouknow．Goodnight．Enjoyyourstayhere． GoodnightIsaidandwiththedeepest20Dwatchedthemgo． 1A．attracted B．pushed C．stopped D．greeted 2A．anger B．sympathy C．courage D．hesitation 3A．lowered B．shook C．broken D．raised 4A．quickest B．biggest C．easiest D．smallest 5A．dealwith B．worryabout C．thinkof D．agreeon 6A．complex B．common C．violent D．serious 7A．increasedto B．calculatedat C．limitedto D．comparedwith 8A．quiet B．lovely C．safe D．attractive 9A．citizen B．manager C．guest D．policewoman 10A．matters B．emergencies C．cases D．relationships 11A．attendedto B．believedin C．reliedon D．fearedfor 12A．that B．which C．what D．who 13A．following B．warning C．avoiding D．leading 14A．powerful B．gentle C．fearless D．confident 15A．simply B．formally C．carelessly D．curiously 16A．pleased B．disappointed C．impressed D．annoyed 17A．forbidden B．persuaded C．allowed D．made 18A．prison B．danger C．trouble D．hospital 19A．crazy B．brave C．active D．lazy 20A．trust B．doubt C．interest D．respect
ExceptfortheIndianstheearliestbackpackersinAmericawerefrontiersmen边民whotraveledthewildernesslookingeitherfornecessitiessuchasfoodandwaterorforsourcesofwealthsuchasfurandgoldForthembackpackingwasawayofsurvivalorameansofachievingwhatonedaywouldbecalledtheAmericanDream．Todayhowevermanypeopleenjoybackpackingasanentertainingactivity．Shoulderingapackandleavingbehindtheworldoftelephonetelevisionandtrafficpromiseanexcitingexperience．Testingone'sstamina耐力andskillsischallengingandregainingasenseofone'splaceinthenaturalworldcanberewarding． Moreoverbackpackingisanactivitythatcanlastanylengthoftimeandcanbeenjoyedaloneorwithfriends．Thentooabackpackingtripmaybeorganizedwithinadayortwo． Thebackpackerandhisfriendshaveonlytodecideontheirdestinationandthenorganizetheall﹣importantequipmentwhosecontentstheymustdependonthetrip．Amapacompassaflashlightalongwithfoodandextraclothingcanbefoundwithoutmuchdifficulty．Oncethebackpackershaveleftwordaboutwheretheygoinanoteontherefrigeratordoororinamessageonanansweringmachinetheycanlookforwardtoanadventurethatwillliftthespiritandpromotethesoul．TheiroutingwillenablethemtoreturninashorttimetotheageoftechnologywiththecourageandindependenceofNattyBumppowhodidindeedbelongtotheageofthefrontier． 1EarlybackpackerswereinterestedinfindingB． A．activitiesinlife B．dailynecessitiesandwealth C．senseoftheirplaceintheworld D．meansofhecomingfamous 2OneoftheadvantagesofbackpackingisthatC． A．itisnotsochallengingasotheractivities B．itdoesnotrequirepeopletodecideonadestination C．itcanhelppeopleconnectwithnature D．itmustbedoneingroupsandcancureone'sloneliness 3ThetextmainlydiscussesD． A．theearlybackpackers B．howtobeabackpacker C．thefutureofbackpacking D．thereasonforpeople'sinterestinbackpacking
若函数fx＝mx3+2x2-3x-1存在单调递增区间则实数m的值可以为
已知F为抛物线y2＝4x的焦点过点F且斜率为1的直线交抛物线于AB两点设|FA|＞|FB|则＝．
假定英语课上老师要求同桌之间交换修改作文请你修改你同桌写的以下作文．文中共有10处语言错误每句中最多有两处．每处错误仅涉及一个单词的增加删除或修改． 增加在缺词处加一个漏字符号∧并在其下面写出该加的词． 删除把多余的词用斜线\划掉． 修改在错的词下画一横线并在该词下面写出修改后的词． 注意1．每处错误及其修改均仅限一词． 2．只允许修改10处多者从第11处起不计分． Iliveinasmallvillageinthecountry．MywifeandIranthevillageshop．Wehaveaverypeacefullifeboredsomeonemightsay．Butweloveit．Weknowallthepeopleinvillageandhaveplentyoftimetostopandchat．Ihaveplentyoftimeformyhobbytoogardeningfishingwalkinginthecountryside．Ilovetheoutdoor'slife．Ididn'talwayslikethisthough．Iusedtohaveaverystressjobworkingtilllateintheofficeeveryeveningandneverbringworkhomeattheweekend．Mywifecomplainedthatheneversawme．AndIhadnotimetofamilylife．Thismademerealizehowwasreallyimportanttome．NowI'mafraidoflookingbacksincethepastlifeseemedahorribledream．
It's3008．Youhaveajobafamilyandyou'reabout40yearsold!Welcometoyourfuturelife． Gettingreadyforworkyoupauseinfrontofthemirror．Turnredyousay．Yourshirtchangesfromskybluetodeepred．Tinypreprogrammedelectronsarerearrangedinyourshirttochangeitscolor．Lookingintothemirroryoufindithardtobelievethatyouare40．Youlookmuchyounger．Withamazingadvancesinmedicinepeopleinyourgenerationmaylivetobe150yearsold．Youarenotevenmiddle﹣aged． AsyougointothekitchenandpreparetopouryourbreakfastcerealintoabowlyouhearToloseweightyoushouldn'teatthatfromyourshoes．Theyreadthetinyelectroniccodeonthecerealboxtofindoutthenutritiondetails．Youdecidetolistentoyourshoes．KitchenwhatcanIhaveforbreakfastAlistofpossiblefoodsappearonthecounteraskitchenchecksitsfoodsupplies． Readyforyourtriptospace．Youaskyoursonanddaughter．In2017onlyspeciallytrainedastronautswentintospace﹣andveryfewofthem．Todayanyonecangotospacefordaytriporlongervacation．Yourbestfriendevenworksinspace．HandingyourchildrenthreestrawberrieseachyouaddThedoctorsaidyouneedtheseforspacetravel．Thankstomedicaladvicevaccinationshotsareathingofthepast．Ordinaryfoodscontainspecificvaccines疫苗．Withtheberriesintheirmouthsthekidsheadforthefrontdoor． It'stimeforyoutogotowork．Yourcarchecksyourfingerprintsandunlocksthedoors．Myofficeautopilot．Youcommand．Yourcardrivesitselfdowntheroadandmovesmoothlyintotrafficonthehighway．Yousitbackandunrollyoure﹣newspaper．Thelatestnewsdownloadsandfillstheviewer．Lookingthroughthepagesyouwatchthenewsasvideofilmsratherthanreadit． 1ThepassageaboveisorganizedinorderofD． A．frequency B．importance C．preference D．time 2Ctransformsthecolorofyourclothingintoanotherin3008． A．Themirror B．Thecounter C．Theclothingitself D．Themedicine 3Theshoesknowthatyoushouldn'teatthebreakfastcerealwiththehelpofA． A．checkingthenutritiondetailsofthefood B．listeningtothedoctor'sadvice C．testingthefoodsuppliesinthekitchen D．pouringthebreakfastintoabowl 4ThestrawberriesthechildreneatserveasD． A．nutrition B．breakfast C．lunch D．vaccines
已知a＞b＞0则下列不等式正确的是
Asweallknowthewarisanancientcustomwhichhasexistedforatleastsixthousandyears.Itwasalwaysevilandusuallyfoolishbutinthepastthehumanracemanagedtolivewithit.Modernskillhaschangedthis.Eithermanwillstopwarorwarwillstopman.Forthepresentitisnuclearweaponsthatcausethegreatestdangerbutbacteriological细菌学的orchemicalweaponsmaybeforelongofferanevengreaterthreat.Isitpossibletopersuademankindtolivewithoutwar?Ifwesucceededinstoppingwartherewouldbenodangerforus.Todothisweneedtopersuademankindtolookuponinternationalquestionsinanewwaynotbycontestsofforceinwhichthevictorygoestothesidewhichismostskillfulinmassacre大屠杀butbyarbitration仲裁inaccordancewithagreedprinciplesoflaw.Itisnoteasytochangeoldmentalhabitsbutthisiswhatmustbeattempted. Therearethosewhosaythattheadoptionofthisorthatideology意识形态wouldpreventwar.Ibelievethistobeacompleteerror.Allideologiesarebaseduponbeliefswithoutproofwhichareatleastdoubtfulandatworsttotallyfalse.Thosepeoplewhobelievethemarewillingtogotowarinsupportofthem. Themovementofworldopinionduringthepasttwoyearshaschangedverylargelysuchaswecanwelcome.Ithasbecomeacommonbeliefthatnuclearwarmustbeavoided.Ofcourseverydifficultproblemsremainintheinternationalworldbutthespiritinwhichtheyarebeingapproachedisabetteronethanitwassomeyearsago.Ithasbeguntobethoughtevenbythepowerfulmenwhodecidewhetherweshallliveordiethatagreementsshouldbereachedevenifbothsidesdonotfindtheseagreementswhollysatisfactory.IthasbeguntobeunderstoodthattheimportantconflictnowadaysisnotbetweenEastandWestbutbetweenManandtheHi﹣techbomb. 1Whatcanwelearnfromthefirstparagraph? A.Wemayfacegreaterthreatfromweapons. B.Nuclearweaponsareworstofall. C.Man'sideaofvictoryhaschanged. D.Dangerousweaponsareforbiddennowadays. 2Theauthorofthepassagebelievethat. A.itisimpossibletolivewithoutwar B.differencesbetweenEastandWestwillleadtowar C.warwillbestoppedbymodernskill D.warmustbestoppedifmanwantstosurvive 3Whichistheonlywaytostopwaraccordingtotheauthor? A.Tostopnuclearweapons. B.Tosettleinternationalissuesthroughagreements. C.Todestroybacteriologicalandchemicalweapons. D.Toletthestrongersidetakeovertheworld. 4Wecaninferfromthelastparagraphthat. A.nuclearwarwilldefinitelynottakeplace B.realagreementshavebeenreachednow C.worldopinionisstilldividedonnuclearwar D.manisbeginningtorealizethatnuclearwaristhegreatestenemy 5Whatdoestheauthorfeelwhilewritingthispassage? A.Hopeful. B.Doubtful. C.Worried. D.Disappointed.
下列有关高尔基体线粒体和叶绿体的叙述正确的是
Whereareyougoingtocollege?I'mgoingtomylocalcommunitycollege.Myanswerseemedtobethemagicphrasethatwouldwipethesmilerightoffmanypeople'sfaces.It'sclearthatpeoplehavealotofmisconceptions误解aboutcommunitycolleges. Manypeoplethinkcommunitycollegesareonlyforpeoplewhocouldn'tgetintoafour﹣yearschool.Butitisnottrue.InhighschoolIalwaysgotA's.ButwhenitcametoapplyingtocollegesIhadnoideawhatIwantedtomajorinandcouldn'tjustifyspendingthousandsofdollarsata4﹣yearschooluntilIknewwhatIwantedtodo.Myparentswereverysupportiveofmydecisiontoattendthecommunitycollege. SomepeoplewillaskSincethecommunitycollegeischeaperwillyougetagoodeducation?Ifoundthatnearlyallofmyprofessorstaughtthesamecoursesat4﹣yearcolleges.MyprofessorswereknowledgeableandexperiencedandIfoundmanyofthecourseschallenging. SomepeoplethinkifIattendthecommunitycollegeIwillmissoutonthecollegeexperience.ImustadmitthatthisissomethingIworriedaboutagreatdealthesummerbeforecollege.ButIsoonlearnedthatthecommunitycollegejustlikeanyothercollegeiswhatyoumakeofit.Istrivedtomakethemostofmytimeatthecommunitycollege.Ialsomadetonsoffriendsbyjoiningclubsandattendingstudentgovernmentmeetings. Itookalotofdifferentcourses.IhadanamazingprofessorwhosuggestedItakeherjournalismclass.NeverhavingwrittenformyhighschoolnewspapersIdarednottakeitbutsinceshewassoenthusiasticIeventuallydecidedtohaveatry.ThatonecoursewasallittookformetorealizethatIwantedtobecomeajournalist. IlookforwardtograduatingthisMaytopursueacareerinbroadcastjournalism.Communitycollegesmaynotbeforeveryonebutformeitisalife﹣changingexperiencethathashelpedmediscoverwhoIamandthepersonIhopetobecome. 1Whatwastheauthor'sparents'attitudetowardshis/herdecisionaboutattendingthecommunitycollege?nomorethan5words 2WhatdoestheunderlinedpartmissoutoninParagraph4mean?1word 3Howdidtheauthormakefriendsatcommunitycollege?nomorethan12words 4Whydaren'ttheauthortakethejournalismclassatfirst?nomorethan12words 5Inyouropinionwhatkindofeffectdoesattendingthecommunitycollegehaveontheauthor?nomorethan15words
Tinyastheyarebatshavetheabilitytoseeinthedarkbyusingaspecialskillcalledecholocation回声定位法.Theymakenoisesandwaitforsoundwavesoranechotobounce反弹backoffobjects.Theycantellthedistanceofvariousobjectsbyhowquicklythesoundwavesbouncebackoffthem.Ifnosoundbouncesbacktheycanthenflyforward. Thisspecialabilityhasbeensimulatedinthehumanworldforalongtimesuchasinsubmarinesandplaneswhosesonar声呐systemsaresomewhatsimilartoecholocation.Butapartfromhelpingvehiclesseewheretheyarewhatifblindpeoplecoulduseecholocationforthemselves?Itturnsoutsomealreadyare. AmericanDanielKishwhoisblindisknownasBatman.Thisisn'tbecausehewalksaroundinacape披风andamaskbutbecausehehasabat﹣likeabilitytolocatewhereheisthroughsharpclickshemakesbymovinghistongueagainsttheroofofhismouth.Kishissoskilledatecholocatingthathecanrideabikeandhikeonhisown. RecentlyresearchcarriedoutattheUniversityofDurhaminEnglandshed揭示somelightonthepowerofhumanecholocation. Kishworkedwithagroupofscientistswhostudiedthewayblindpeoplelistentotheechoesthattheyproducefromclicks. Theteamwhichconductedexperimentswithothervolunteersfoundthatpeoplewerecapableofhearingevenveryfaintechoesonesfarfainterthanhadbeenpreviouslythought. SpeakingtoTheIndependentLoreThalerleadscientistofthegroupsaidWefoundthatinsomeconditionstheywerereallyfaint﹣about95percentsofterthantheactualclicksbuttheecholocatorswerestillabletosensethis. AndrewKolarikoftheUniversityofCambridgeisanotherexpertinecholocation.ReactingtotheDurhamstudyhetoldBBCNewsthatecholocationcanbeveryusefulatprovidinginformationatfaceorchestheightandcouldhelppeopleavoidobjectslikelowhangingbranchesthatmightnotgetdetectedbythecane盲杖oraguidedog. AlthoughKish'sskillisremarkablethere'shopeforotherblindpeoplewhowanttouseecholocation.AccordingtoBBCNewsecholocationisaskillblindpeoplecanacquireanddevelopjustlikelearningalanguage.AsKolariksaidTeachingecholocationskillscouldprovideblindpeoplewiththemeansofexploringnewplaces. 1TheunderlinedwordsimulatedinParagraph2probablymeans. A.copied B.discovered C.improved D.challenged 2HowdoesKishlocatewhereheis? A.Byusinghisgreatsenseofhearing B.Bylisteningtotheechoesproducedbyhiscane. C.Viathesonarsystemattachedtohisbody. D.Viatheechoesfromtheclickshemakeswithhistongue. 3WhatdidLoreThaler'steamfindfromtheirstudies? A.Itishardforecholocatorstosensefaintechoes. B.Humanscanecholocatebetterthanwethoughtwecould. C.Echolocatorscanpickupalltypesofechoes. D.Blindpeoplearebetterecholocatorsthanthosewhocansee. 4Accordingtothearticleteachingecholocationtoblindpeople. A.isnoteasytoputintopractice B.willenablethemtogetridoftheircane C.willopenupnewpossibilitiesforthem D.willimprovetheirabilitytolearnanewlanguage 5Whatisthearticlemainlyabout? A.Differenttypesofhumanecholocation. B.Theimportanceofhumanecholocation. C.Studiesonblindpeopleusingecholocation. D.Whybats'echolocationcouldbeusedbyhumans.
回答下列与种群数量有关的问题． 1将某种单细胞菌接种到装有10mL液体培养基培养基M的试管中培养并定时取样进行计数．计数后发现试管中该种菌的总数达到a时种群数量不再增加．由此可知该种群增长曲线为型且种群数量为时种群增长最快． 2若将该种菌接种在5mL培养基M中培养条件同上则与上述实验结果相比该种菌的环境容纳量K值填“增大”“不变”或“减小”．若在5mL培养基M中接种该菌的量增加一倍则与增加前相比K值填“增大”“不变”或“减小”原因是．
Youcangetalotfrombeinghealthy．Everyoneneedstotaketimetoexercise．1DHerearesometipsonhowtomakebetteruseofyourfreetimewhilestayinghealthy． 2GMakesurethatyourjoints关节andbodyorgansarekeptingoodworkingorder．Exercisecanalsohelpkeepyourweightatahealthylevelandcanprotectyoufromcatchingcoughsandcolds．Otherbenefitsareanincreaseinyourenergylevelandbrainactivity．Knowingthatyou'relookingandfeelinggoodcanalsoincreaseyourself﹣confidence．Ifyou'reunder18youshouldtrytodoatotalof60minutesofphysicalactivityeveryday．Thisincludesanythingfromtakingtheliftatthegymtowalkingupstairs．3A Gettingfitisn'tallaboutgyms﹣someformsofexercisewon'tcostyouanymoneyandmostformscanbeeasilyusedinyourbusylifewithouttakingsomespecialtimeinyourday．4C 5EPlayingteamsportslikefootballorbasketballisgreatexerciseanditisoftenmoreenjoyablebecauseyou'replayingwithagroupoffriends． A．Anygrown﹣upneedsatleasthalfanhourofexerciseatleastfivedaysaweek． B．Don'tdoexerciseifyouarebusy． C．Forexampleridingabiketoschoolorworkcanimproveyourfitnesslevel． D．Therearelotsofwaystoimproveyourhealth． E．Gettingfitisn'tjustsomethingyouhavetodobyyourself． F．Oneshouldtrytosavemoneyforjoiningagym． G．Keepingphysicallyactiveisbeneficial．
复数z＝1-ii为虚数单位的虚部为
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