版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
英语专业四级听力50篇1.TownandCountryLifeinEngland
ThereisabigdifferencebetweentownlifeandcountrylifeinEngland.Inthecountry,everybodyknowseverybodyelse.Theyknowwhattimeyougetup,whattimeyougotobedandwhatyouhavefordinner.Ifyouwanthelp,youwillalwaysgetitandyouwillbegladtohelpothers.
InalargetownlikeLondon,however,itcansometimeshappenthatyouhaveneverseenyournextdoorneighborandyoudonotknowhisnameoranythingabouthim.PeopleinLondonareoftenverylonely.Thisisbecausepeoplegotodifferentplacesintheeveningsandatweekends.IfyouwalkthroughthestreetsinthecentreofLondononSunday,itislikeatownwithoutpeople.Oneissorryforoldpeoplelivingontheirown.Theycoulddieintheirhomesandwouldnotbediscoveredforweeksorevenmonths.2.AChangeinWomen’sLife
Theimportantchangeinwomen’slife-patternhasonlyrecentlybeguntohaveitsfulleffectonwomen’seconomicposition.Evenafewyearsagomostgirlsleftschoolatthefirstopportunity,andmostofthemtookafull-timejob.However,whentheymarried,theyusuallyleftworkatonceandneverreturnedtoit.Todaytheschool-leavingageissixteen,manygirlsstayatschoolafterthatage,andthoughwomentendtomarryyounger,moremarriedwomenstayatworkatleastuntilshortlybeforetheirfirstchildisborn.Verymanymoreafterwardsreturntofull-timeorpart-timework.Suchchangeshaveledtoanewrelationshipinmarriage,withthehusbandacceptingagreatershareofthedutiesandsatisfactionsoffamilylifeandwithbothhusbandandwifesharingmoreequallyinprovidingthemoney,andrunningthehome,accordingtotheabilitiesandinterestsofeachofthem.3.APopularPastimeoftheEnglishPeople
Oneofthebestmeansofunderstandingthepeopleofanynationiswatchingwhatthedowiththeirnon-workingtime.
MostEnglishmen,womenandchildrenlovegrowingthings,especiallyflowers.VisitorstoEnglandinspring,summerorautumnarelikelytoseegardensalltheywayalongtherailwaylines.Thereareflowersattheairportsandflowersinfactorygrounds,aswellasingardensalongtheroads.EachEnglishtownhasatleastoneparkwithbeautifullykeptflowerbeds.Publicbuildingsofeverykindhavebrilliantwindowboxesandsometimesbasketsofflowersarehangingonthem.
ButwhattheEnglishenjoymostisgrowingthingsthemselves.Ifitisimpossibletohaveagarden,thenawindowboxorsomethinggrowinginapotwilldo.Lookingateachother’sgardensisapopularpastimewiththeEnglish.
UsefulWordsandExpressions:
1.windowbox:窗台上的花盆箱
2.pastime消遣,娱乐
Swimmingismyfavoritepastime.4.BritishandAmericanPoliceOfficers
Realpolicemen,bothinBritainandtheU.S.,hardlyrecognizeanycommonpointsbetweentheirlivesandwhattheyseonTV—iftheyevergethomeintime.
Somethingsarealmostthesame,ofcourse,butthepolicemendonotthinkmuchofthemmuchofthem.
Thefirstdifferenceisthatapoliceman’sreallifedealswiththelaw.Mostofwhathelearnsisthelaw.Hehastoknowactuallywhatactionsareagainstthelawandwhatfactscanbeusedtoprovethemincourt.Hehastoknownearlyasmuchlawasalawyer,andwhat’smore,hehastoputitintopracticeonhisfeet,inthedarkand,runningdownanarrowstreetaftersomeonehewantstotalkto.
Littleofhistimeisspentintalkingwithbeautifulgirlsorinbravelyfacingcruelcriminals.Hewillspendmostofhisworkinglifearrangingmillionsofwordsonthousandsofformsabouthundredsofsad,ordinarypeoplewhoareguilty---ornotofstupid,unimportantcrimes.
UsefulWordsandExpressions:
1.
thinkmuchof重视,尊重
2.
incourt在法庭上
3.
criminal罪犯,犯罪者
4.
guilty犯罪的,有罪的5.LivingSpace
Howmuchlivingspacedoesapersonneed?Whathappenswhenhisspaceneedsarenotmet?Scientistsaredoingexperimentsonratstotrytodeterminetheeffectsofovercrowdedconditionsonman.Recentstudieshaveshownthatthebehaviorofratsisgreatlyaffectedbyspace.Ifratshaveenoughlivingspace,theyeatwell,sleepwellandproducetheiryoungwell.Butiftheirlivingconditionsbecometoocrowded,theirbehaviorandeventheirhealthchangeobviously.Theycannotsleepandeatwell,andsignsoffearandworrybecomeclear.Themorecrowdedtheyare,andmoretheytendtobiteeachotherandevenkilleachother.Thus,forrats,populationsandviolencearedirectlyrelated.Isthisanaturallawforhumansocietyaswell?Isenoughspacenotonlysatisfactory,butnecessaryforhumansurvival?Theseareinterestingquestions.6TheUnitedNations
In1945,representativesof50nationsmettoplanthisorganization.ItwascalledtheUnitedNations.Afterthewar,manymorenationsjoined.
TherearetwomajorpartsoftheUnitedNations.OneiscalledtheGeneralAssembly.IntheGeneralAssembly,everymembernationisrepresentedandhasanequalvote.
ThesecondpartiscalledtheSecurityCouncil.Ithasrepresentativesofjust15nations.Fivenationsarepermanentmembers:theUnitedStates,Russia,France,Britain,andChina.The10othermembersareelectedeverytwoyearsbytheGeneralAssembly.
ThemajorjoboftheSecurityCouncilistokeeppeaceintheworld.Ifnecessary,itcansendtroopsfrommembernationstotrytostoplittlewarsbeforetheyturnintobigones.
ItishardtogetthenationsoftheSecurityCounciltoagreeonwhenthisisnecessary.Buttheydidvotetotrytostopwars.
UsefulWordsandExpressions:
1.
representative代表
2.
GeneralAssembly联合国大会
3.
permanent永久的,持久的
4.
SecurityCouncil联合国安全理事会7Plastic
Weuseplasticwraptoprotectourfoods.Weputourgarbageinplasticbagsorplasticcans.Wesitonplasticchairs,playwithplastictoys,drinkfromplasticcups,andwashourhairwithshampoofromplasticbottles!
Plasticdoesnotgrowinnature.Itismadebymixingcertainthingstogether.Wecallitaproducedormanufacturedmaterial.Plasticwasfirstmadeinthe1860sfromplants,suchaswoodandcotton.Thatplasticwassoftandburnedeasily.
Thefirstmodernplasticsweremadeinthe1930s.Mostclearplasticstartsoutasthick,blackoil.Thatplasticcoatinginsideapanbeginsasnaturalgas.
Overtheyears,hundredsofdifferentplasticshavebeendeveloped.Somearehardandstrong.Somearesoftandbendable.Someareclear.Somearemany-colored.Thereisaplasticforalmosteveryneed.Scientistscontinuetoexperimentwithplastics.Theyhopetofindevenwaystousethem!8DisplayofGoods
Aresupermarketsdesignedtopersuadeustobuymore?
Freshfruitandvegetablesaredisplayednearsupermarketentrances.Thisgivestheimpressionthatonlyhealthyfoodissoldintheshop.Basicfoodsthateveryonebuys,likesugarandtea,arenotputneareachother.Theyarekeptindifferentaislessocustomersaretakenpastotherattractivefoodsbeforetheyfindwhattheywant.Inthisway,shoppersareencouragedtobuyproductsthattheydonotreallyneed.
Sweetsareoftenplacedatchildren’seyelevelatthecheckout.Whileparentsarewaitingtopay,childrenreachforthesweetsandputtheminthetrolley.
Moreisboughtfromafifteen-footdisplayofonetypeofproductthanfromaten-footone.Customersalsobuymorewhenshelvesarefullthanwhentheyarehalfempty.Theydonotliketobuyfromshelveswithfewproductsonthembecausetheyfeelthereissomethingwrongwiththoseproductsthatarethere.
UsefulWordsandExpressions:
1.
aisle走廊,过道
2.
trolley手推车
3.
checkout收款台9AlbertEinstein
AlbertEinsteinwasborninGermanyin1879,Hisfatherownedafactorythatmadeelectricaldevices.Hismotherenjoyedmusicandbooks.HisparentswereJewishbuttheydidnotobservemanyofthereligion’srules.Albertwasaquitechildwhospentmuchofhistimealone.Hewasslowtotalkandhaddifficultylearningtoread.WhenAlbertwasfiveyearsold,hisfathergavehimacompass.Thechildwasfilledwithwonderwhenhediscoveredthatthecompassneedlealwayspointedinthesamedirection—tobenorth.Heaskedhisfatherandhisunclewhatcausedtheneedletomove.Theiranswersaboutmagnetismandgravityweredifficultfortheboytounderstand.Yethespentalotoftimethinkingaboutthem.Hesaidlaterthathefeltsomethinghiddenhadtobebehindthings.
Usefulexpressionsandwords:
1.
device装置,设备
leavetoone’sowndevices听任某人自行其是,允许某人按自己的意愿做事
Sheleftthechildtoherowndevicesforanhourintheafternoon.
她允许孩子在下午有一个小时的自由支配时间。
2.compass指南针
beyondone’scompass某人力所不及
catch/fetch/takeacompass兜圈子,绕道,拐弯抹角
keepsthwithincompass把某种事物限制在适当的范围内
speakwithincompass谨慎小心地说
withinsb’scompass某人力所能及的
withinthecompassof在……范围内
3.magnetism磁力10PrivateCars
Withtheincreaseinthegeneralstandardofliving,someordinaryChinesefamiliesbegintoaffordacar.Yetopinionsofthedevelopmentofaprivatecarvaryfrompersontoperson.
Itgivesamuchgreaterdegreeofcomfortandmobility.Theownerofacarisnolongerforcedtoreplyonpublictransport,andhencenoirritationcausedbywaitingforbusesortaxis.However,othersstronglyobjecttodevelopingprivatecars.Theymaintainthatasmoreandmorecarsareproducedandruninthestreet,alargevolumeofpoisonousgaswillbegivenoff,pollutingtheatmosphereandcausingactualharmtothehealthofpeople.
WhetherprivatecarsshouldbedevelopedinChicagoisadifficultquestiontoanswer,yetthedesireforthecomfortandindependenceaprivatecarcanbringwillnotbeeliminated.11.AHenpeckedHusbandandHisWife
Therewasoncealarge,fatwomanwhohadasmall,thinhusband.HehadajobinabigcompanyandwasgivenhisweeklywageseveryFridayevening.AssoonashegothomeonFridays,hiswifeusedtomakehimgiveherallhismoney,andthensheusedtogivehimbackonlyenoughtobuyhislunchinhiscompanyeveryday.
Oneday,thesmallmancamehomeveryexcited.Hehurriedintotheliving-room.Hiswifewaslisteningtotheradioandeatingchocolatesthere.
“Youwillneverguesswhathappenedtometoday,dear.”hesaid.
Hewaitedforafewsecondsandthenadded,“Iwontenthousanddollarsonthelottery!”
“Thatiswonderful!”saidhiswifedelightedly.Butthenshepulledalongfaceandaddedangrily,“Buthowcouldyouaffordtobuytheticket?”
UsefulWordsandExpressions:
1.
henpecked怕老婆的,妻管严的
2.
lottery彩票
agreatlottery虚无缥缈的事
3.
pullalongface拉下脸来
haveafacetosaythat脸皮厚得竟能讲出这种话12.AYoungMan’sPromise
Oneday,ayoungmanwaswritingalettertohisgirlfriendwholivedjustafewmilesawayinanearbytown.Hewastellingherhowmuchhelovedherandhowwonderfulhethoughtshewas.Themorehewrotethemorepoetichebecame.Finallyhesaidthatinordertobewithher,hewouldsufferthegreatestdifficulties,hewouldfacethegreatestdangersthatanyonecouldn’timagine.Infact,tospendonlyoneminutewithher,hewouldswimacrossthewidestriver,hewouldenterthedeepestforest,andhewouldfightagainstthefiercestanimalswithhisbarehands.
Hefinishedtheletter,signedhisnameandthensuddenlyrememberedthathehadforgottentomentionsomethingquiteimportant.So,inapostscriptbelowhisname,headded:
“Bytheway,I’llbeovertoseeyouonWednesdaynight,ifitdoesn’train.”
13.AKindNeighbor
Mr.andMrs.Jones’apartmentwasfullofluggage,packages,furnitureandboxes.Bothofthemwereverybusywhentheyheardthedoorbellring.Mrs.Joneswenttoopenitandshesawamiddle-agedladyoutside.Theladysaidshelivednextdoor.Mrs.Jonesinvitedhertocomeinandapologizedbecausetherewasnoplaceforhertosit.“Oh,that’sOK.”saidthelady.“Ijustcometowelcometoyournewhome.Asyouknow,insomepartsofthiscity,neighborsarenotfriendlyatall.Theyaresomeapartmenthouseswherepeopledon’tknowanyoftheirneighbors,noteventheonesnextdoor.Butinthisbuilding,everyoneisveryfriendlywitheveryoneelse.Weareabighappyfamily.Iamsureyouwillbeveryhappyhere.”Mr.andMrs.Jonessaid,“Butmadam,wearenotnewdwellersinthisapartment.We’velivedherefortwoyears.Wearemovingouttomorrow.”14.ThatIsn’tOurFault
Mr.andMrs.Williamsgotmarriedwhenhewastwenty-three,andshewastwenty.Twenty-fiveyearslater,theyhadabigparty,andaphotographercameandtooksomephotographsofthem.
ThenthephotographergaveMrs.Williamsacardandsaid,“They’llbereadynextWednesday.Youcangetthemfromstudio.”
“No,”Mrs.Williamssaid,“pleasesendthemtous.”
Thephotographsarrivedaweeklater,butMrs.Williamswasnothappywhenshesawthem.Shegotintohercaranddrovetothephotographer’sstudio.Shewentinsideandsaidangrily,“Youtooksomephotographsofmeandmyhusbandlastweek,butI’mnotgoingtopayforthem.”
“Oh,whynot?”thephotographerasked.
“Becausemyhusbandlookslikeamonkey,”Mrs.Williamssaid.
“Well,”thephotographeranswered,“thatisn’tourfault.Whydidn’tyouthinkofthatbeforeyoumarriedhim?”15.AGuide’sAnswer
In1861,theCivilWarstartedintheUnitedStatesbetweentheNorthernandtheSouthernstates.Thewarcontinuedwithgreatbitternessuntil1865,whentheNorthernerswerevictorious.However,eventoday,manySouthernershavenotforgottentheirdefeat,orforgiventheNortherners.
Afewyearsago,apartyofAmericantouristsweregoingroundoneofthebattlefieldsoftheCivilWarwithaguidewhocamefromoneoftheSouthernstates.Ateachplace,theguidetoldthetouristsstirringstoriesabouthowafewSouthernsoldiershadconqueredpowerfulforcesofNorthernersthere.
Atlast,oneofthetourists,aladywhocamefromtheNorth,stoppedtheguideandsaidtohim,“ButsurelythattheNorthernarmymusthavewonatleastonevictoryintheCivilWar?”
“NotaslongasI’mtheguidehere,madam,”answeredtheSouthernguide.16.AQualifiedPilot
Thecaptainofasmallshiphadtogoalongarockycoast,buthewasunfamiliarwithit,sohetriedtofindaqualifiedpilottoguidehim.Hewentashoreinoneofthesmallports,andalocalfishermanpretendedthathewasapilotbecauseheneededsomemoney.Thecaptaintookhimonboardandaskedhimwheretosteertheship.
Afterhalfanhour,thecaptainbegantosuspectthatthefishermandidnotreallyknowwhathewasdoingandwherehewasgoing.
“Areyousureyouareaqualifiedpilot?”heasked.
“Oh,yes,”answeredthefisherman.“Iknoweveryrockonthispartofthecoast.”
Suddenlytherewasaterriblecrashfromundertheship.Atoncethefishermanadded,“Andthat’soneofthem.”17.LivingThingsReactYouandallorganismsliveanenvironment.Anenvironmentismadeupofeverythingthatsurroundsanorganism.Itcanincludetheair,thewater,thesoil,andevenotherorganisms.Anorganismrespondstochangesinitsenvironment.Whenanorganismrespondstoachange,itreactsincertainways.Alllivingthingsrespondinsomeway.Haveyouevernoticedhowplantsandinsectsrespondtolight?Plantsbendtowardlight.Insectsflytowardlight.Livingthingsalsorespondinotherways.Theleavesonsometreesrespondtoachangeinseason.Inautumn,theychangecolorsandthenfalloffthebranchesAnimalsalsorespondtoachangeinseason.Squirrelssavenutsforthewinter.Bearssleepthroughthewinterinacave.Yourespondtoyourenvironmentinmanyways,too.Youmayshiverifyouarecold.Whatotherwaysdoyourespondtochangesinyourenvironment?18.FloweringPlants
Whatarethepartsofaflower?
Flowerscanhavemalepartsandfemaleparts.Thefemalepartsmakeeggsthatbecomeseeds.Themalepartsmakepollen.Pollenisapowderymaterialthatisneededbytheeggstomakeseeds.Tomakeseeds,pollenandeggsmustcometogether.Thewind,insects,andbirdsbringpollentoeggs.Manyanimalsloveflowers’brightcolors.Theyalsolikeasugaryliquidinflowers.Thisiscallednectar.Whiletheydrinknectar,pollenrubsoffontheirbodies.Astheymove,someofthispollengetsdeliveredtothefemaleflowerparts.
Overtime,thefemalepartsturnintofruitsthatcontainseeds.Animalsofteneatthefruitsandtheseedspassthroughtheirbodiesaswaste.Theanimalsdonoknowtheyareworkingfortheplantsbyplantingseedsastheytraveltodifferentplaces!
UsefulwordsandExpressions:
1.
flowering开花的
2.
pollen花粉
3.
powdery粉状的
4.
sugar含糖的,甜的
5.
nectar花蜜,甘露
6.
rub磨擦(19)FindingtheDirectionandLocationHowcanyoutellwhichdirection?Byday,lookfortheSun.Itisintheeastinthemorningandthewestintheafternoon.Atnight,usetheBigDippertohelpyoufindtheNorthStar.Itwouldbebettertobringacompassbecauseitsneedlealwayspointsnorth.
Howdoyouknowhowfaryouhavegone?Youcouldcounteverystep.Eachstepisabouttwofeet.You’dbetterwearapedometerwhichisatoolthatcountssteps.Ifyouknowwhereyoustarted,whichdirectionyouareheading,andhowfaryouhavegone,youcanuseagoodmaptofigureoutexactlywhereyouare.
Todaythereisanewwayfortravelerstofigureoutwheretheyare.ItistheGPS.Ithas24satellitesthatorbittheearthandconstantlybroadcasttheirpositions.SomedayyoumaycarryasmallreceiverasyouhikeanduseGPStofindoutifyouarethereyet!UsefulWordsandExpressions:
1.
dipper北斗七星
2.
compass罗盘
3.
pedometer步数计
4.
GPS=GlobalPositionSystem全球定位系统
5.
orbit轨道,绕……轨道而行
6.
receiver接收器(20)WavesHowdoeslightgetfromthesuntotheearth?Howdoesmusicgetfromthestagetotheaudience?Theymovethesameway-----inwaves!
Lightandsoundareformsofenergy.Allwavescarryenergy,buttheymaycarryitdifferently.Lightandsoundtravelthroughdifferentkindsofmatter.Forexample,lightwavescannotmovethroughwalls,butsoundwavescan.Thatiswhyyoucanhearpeopletalkinginanotherroomeventhoughyoucannotseethem.Theenergyofsomewavesisdestructive.Anearthquakeproducesseismicwaves.
Catchawave.Askafriendtostandafewfeetawayfromyou.Stretchaspringbetweenyou.Shakethespringtotransferenergytoit.Whathappens?Thespringbouncesupanddowninwaves.Whenthewavesreachyourfriend,theybouncebacktoyou!
Lightwavestravel300,000kilometers(186,000miles)persecond!Theycanalsotravelthroughavacuum.Thatiswhylightfromthesunanddistantstarscantravelthroughspacetotheearth!(21)SoilsTherearemanydifferentkindsofsoils.Differentsoilshavedifferenttypesofrockandmineralsinthem.Somesoilshavemorewaterinthemthanothers.Somesoilsmighthavemoreplantandanimalmaterialinthem,too.
Differentkindsofsoilsarefoundindifferentpartsoftheworld.ThereareseveralkindsofsoilsfoundintheUnitedStates.Insomeareas,thesoilhasalotofclay.Othersoilsareverysandy.Loamisakindofsoilthathasagoodmixtureofclayandsand.
Insomeplaces,soillayersareverythick.Lotsofplantsgrowinplaceswithathicksoillayer.Indryandwindyplacessoillayersaremuchthinner.Layersofsoilonmountainsarethinbecausegravitypullsthesoildownhill.
Thetypeofsoilinaparticularplaceaffectswhatkindsofplantscangrowthere.
UsefulWords:
1.
clay黏土,泥土
2.
loam肥土
3.
layer层
4.
gravity地心引力,重力
5.
downhill往下(22)CrisisLifeisacontest!Whowillwin?Abluebirdandsparrowbothcompeteforspacetobuildtheirnests.Afast-growingmapletreeandslower-growingdogwoodcompeteforthesunlighttheybothneed.Oilcompeteswithcoalandnuclearpowerasanenergysourceforelectricpowerplants!
Thereisaproblem.Thereisalimitedamountofspaceforbirds,sunlightfortrees,andenergyforpeople!Ifwedonotcutbackonourusesofsomeofourresources,somedaytheywillbegone!
Howcanweuseenergytodayandknowwewillhaveenoughtogoaroundinthefuture?Wecanchoosealternate,orreplacement,energyresources.Ittakestheearthmillionsofyearstocreatecoal,oil,andgas.Theyarenonrenewableresources.
Solarenergy,windenergyandwaterenergyarerenewableresources.Ittakestheearthmillionsofyearstocreatecoal,oil,andgas.Theyarenonrenewableresources.
Solarenergy,windenergyandwaterenergyarerenewable.Whatotherwayscanweconserveoursources?Howcanwemakesurethereisalwaysenoughtogoaround?
Usefulwordsandexpressions:
1.
bluebird蓝知更鸟
2.
sparrow麻雀
3.
dogwood山茱萸
4.
powerplant发电厂,发电站
5.
altern
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 校园欺凌工作报告制度
- 护理技术操作考核总结和评价
- 成长足迹听说之旅人教版八下英语第三单元
- 结构静力分析的基本方法力学
- 2026年人教版高中地理人口与城市分布测试卷及答案
- 人教版初中英语八年级上册第7单元词汇练习题及答案
- 语文第七单元字词复习
- 2026年北师大版高中英语高二年级第4单元阅读理解专项训练习题及答案
- 澳优未来品牌规划091103 NXPowerLite
- 焊接方法与设备焊接电弧
- (正式版)DB15∕T 1932-2020 《公路抗凝冰沥青混合料设计与施工技术规范》
- 桡骨茎突狭窄性腱鞘炎22课件
- 《建筑施工技术》课件-第三章 砌筑工程
- 世界毒品报告
- 2025年MySQL数据类型试题及答案
- GB/T 34110-2025信息与文献文件(档案)管理核心概念与术语
- 2025年湖北行测试题及答案
- 《商法(第七版)》课件全套 赵万一
- 化学废液处理协议书范本
- 波动率微笑(宽客大师教你建模)
- AIGC提示词美学定义
评论
0/150
提交评论