Unit8復(fù)習(xí)講義牛津譯林版八年級英語下冊_第1頁
Unit8復(fù)習(xí)講義牛津譯林版八年級英語下冊_第2頁
Unit8復(fù)習(xí)講義牛津譯林版八年級英語下冊_第3頁
Unit8復(fù)習(xí)講義牛津譯林版八年級英語下冊_第4頁
Unit8復(fù)習(xí)講義牛津譯林版八年級英語下冊_第5頁
已閱讀5頁,還剩7頁未讀, 繼續(xù)免費(fèi)閱讀

下載本文檔

版權(quán)說明:本文檔由用戶提供并上傳,收益歸屬內(nèi)容提供方,若內(nèi)容存在侵權(quán),請進(jìn)行舉報(bào)或認(rèn)領(lǐng)

文檔簡介

8BUnit8Agreenworld一、icstripandWeletotheunit.1.begoingtodosth.打算做某事【例句】The

money

we

raise

willbegoing

to

avery

worthy

cause.

我們籌集的錢款將用于非常崇高的事業(yè)。2.Moretreeswillbeplanted.將要種更多的樹。【將來時(shí)的被動(dòng)語態(tài)】中考鏈接:Thework________(finish)inoneweek.3.begoodfor…對……有好處begoodat意為“擅長”?!纠洹縏akingexerciseisgoodforhealth.運(yùn)動(dòng)對健康有益。AreyougoodatEnglish?你擅長英語嗎?【詞組】beweakin在某方面薄弱/不擅長dowellin=begoodat擅長doharmto=beharmfulto多某某有害中考鏈接:()Tomisgood_______playingfootball.Itisgood_______hishealth.A.at;forB.for;forC.at;at D.for;at4.likedigginginthegarden喜歡在花園里挖地★dig→過去式:dug→過去分詞:dug→現(xiàn)在分詞:digging中考鏈接:Afterashortrest,theworkerscarriedon______(挖)holesontheground.5.plantbreadfruittrees種植水果面包樹6.Areyouserious?你是認(rèn)真(嚴(yán)肅)的嗎?7.reduceairpollutionbyridingbicycles通過騎自行車減少空氣污染8.savewaterbytakingshortershowers通過縮短淋浴時(shí)間來節(jié)約用水9.saveenergybyturningoffthelights通過關(guān)燈來節(jié)約能源10.protecttheenvironmentbyrecyclingwaste通過回收垃圾來保護(hù)環(huán)境11.liveagreenlife過綠色生活【liveahappylife過幸福生活】12.drivemetoschool開車送我去上學(xué)13.causeseriousairpollution引起嚴(yán)重的空氣污染★beseriousabout…對…認(rèn)真

【例句】Beserious

about

your

connection

to

Spirit.

認(rèn)真對待你與心靈的聯(lián)系。中考鏈接:IfailedmyMathsexamagain.Ithinkyoushouldbes_________aboutMathslater.14.It’swiseforpeopletochoosepublictransportorridebicycles.對人們來說選擇公共交通或騎自行車是明智的。二、Reading1.trytokeepitthatway盡力讓它保持原來那樣thatway意為“這樣;那樣;那邊”。way可以和this、that等連用?!纠洹縒hydoesheactthisway?他為什么這樣做?中考鏈接:Wecangethishelpinthatw_______.2.beseparatedintodifferentgroups被分成不同的類群separate...into....把......分成........(若干部分) 練習(xí):Thewaste_______(separate)intodifferentgroupsbeforebeingthrownintothebinThetwinswere________(分開)inthewar.Theyfinallygottogether40yearslater.Insomeforeigncountries,thingslikeglass,plasticandpaperareusually________intodifferentgroupsandthenrecycled.3.anorganizationforrecyclingclothes一個(gè)回收舊衣服的組織4.collectoldclothesfromallover(=around)thecountry收集來自全國的舊衣服5.Someoftheclothesaresoldincharityshops,somearegiventothepoor,andothersaresenttofactoriesforrecycling.【some....,some.....,others......】6.havemanylawstoprotecttheenvironment有許多法律來保護(hù)環(huán)境7.Wearenotallowedtocutdowntrees.我們不被允許砍伐樹木。★①allowsb.todosth.允許某人做某事→sb.beallowedtodosth.某人被允許做某事★②allowdoingsth.允許做某事。中考鏈接:Mybossdoesnotallowme______(use)themobilephone.Weareonlyallowed______(smoke)inthishouse.★③cutdown砍伐,砍下【動(dòng)副詞組,代詞放中間】中考鏈接:()Thetreeisdead.Please_______.A.cutdownitB.cutitdownC.cutitoutD.cutoutit8.bepunished被懲罰9.befined被罰款10.limitairandwaterpollution限制空氣和水污染11.dependonitsrichresources依靠它豐富的資源★【重點(diǎn)】dependonsth./sb.依靠某物/某人【擴(kuò)展】berichin....富含....e.g:TomatoesarerichinVitaminC.西紅柿富含維C.中考鏈接:Youshouldavoidd______onyourparents.12.protectitwisely明智地保護(hù)它wiseadj.明智的wiselyadv.明智地wisdomn.智慧中考鏈接:Afterreadingthetouchingstory,IknowIshouldspendmymoney________(明智地).13.useenergyfromthesun使用來自太陽的能量14.Thesenewtypesofenergycostverylittle.這些新型能源成本很低(花錢少)中考鏈接:()Thebike_______himabout350yuanyesterday.A.spentB.costC.tookD.paid15.★runout用光;耗盡(無被動(dòng))=beusedupThetimewillrunout.=Thetimewillbeusedup.runout和runoutof這兩個(gè)短語都有“用完”的意思,但用法不同。runout作不及物短語,表示“被用完;被耗盡;(人)把東西用完(或花光)”,其主語通常是時(shí)間、金錢、食物等無生命名詞,而runoutof則是及物短語,表示主動(dòng),其主語通常為人。【例句】Mymoneyisrunningout.我的錢快用完了。中考鏈接:()Isthetime_______?A.runoutB.runningoutC.runningoutof D.ranout()I'mafraidthatthistypeofenergywillifwecontinuetowasteit.A.runout B.breakout C.edown D.falldown()Theenergyfromthesunandthewindisverycheapanditwillnever________.A.eoutB.putoutC.getoutD.runout()―Wemusttakeactiontoprotectourearthrightnowastimeis_______.―Yes.Let'sgetstarted.ingoutB.goingoutC.puttingoutD.runningout16.producelittlepollution產(chǎn)生很少的污染【produce動(dòng)詞:生產(chǎn);產(chǎn)生】【擴(kuò)展】product名詞:產(chǎn)品;production名詞:產(chǎn)量17.WorldEnvironmentDay世界環(huán)境日18.Rememberthateveryonecandosomethingtomakeadifference.請記住每個(gè)人都能做些事來(對環(huán)境)產(chǎn)生影響/起到作用。★①makeadifferencetosb./sth.對某人/某物產(chǎn)生影響/起到作用【to為介詞】

【例句】Itis

never

toolate

tomakea

difference

to

our

environment.

為我們的環(huán)境做出的任何改變永遠(yuǎn)都不嫌晚。擴(kuò)展:makeadifferencetodoingsth.【to為介詞】★②different(adj)→difference(n.)19.Whatdotheydowitholdclothes?他們?nèi)绾翁幚砼f衣服?=Howdotheydealwitholdclothes?【回顧】what....dowith....?=how....dealwith......?如何處理......?三、Grammar:一般將來時(shí)的被動(dòng)語態(tài)。【語法】A.一般將來時(shí)的被動(dòng)語態(tài):結(jié)構(gòu):willbe+過去分詞或am/is/aregoingto+過去分詞Eg:①Theshowwillbeheldinthetownsquare.②Alotofactivitiesaregoingtobeorganizednextweek.【語法】B.特殊句型的被動(dòng)語態(tài):含有使役動(dòng)詞(make/let/have)或感官動(dòng)詞(hear,see,listento,lookat,find,watch,feel等)的句子,在主動(dòng)語態(tài)中這些詞后常跟不帶to的動(dòng)詞不定式,但是在改成被動(dòng)語態(tài)時(shí),則一定要把省去的to再加上去,另外help這一個(gè)詞在主動(dòng)語態(tài)中后面的動(dòng)詞不定式可以帶to,也可不帶to,但在被動(dòng)語態(tài)中也必須把to加上去。例:①M(fèi)otheroftenmakesmedosomehousework.→Iamoftenmadetodosomehouseworkbymother.②Wesawhimrunintotheclassroom.→Hewasseentorunintotheclassroombyus.teach,give,pass,show,buy,tell等動(dòng)詞常常帶有兩個(gè)賓語(雙賓語:直接賓語和間接賓語),改為被動(dòng)語態(tài)時(shí),兩個(gè)賓語可以選其中任一個(gè)作主語。如果直接賓語被提前作主語,那么間接賓語(一般是人)前要加相應(yīng)的介詞to/for。例:①Shegavemeapen.=Shegaveapentome.→Iwasgivenapenbyher.→Apenwasgiventomebyher.②Myfatherboughtmeanewbike.=Myfatherboughtanewbikeforme.→Iwasboughtanewbikebymyfather.→Anewbikewasboughtformebymyfather.由不及物動(dòng)詞(vi)+介詞/副詞+賓語的句子改成被動(dòng)語態(tài)時(shí),介詞或副詞不能丟掉例:①Weshouldspeaktooldpeoplepolitely.→Oldpeopleshouldbespokentopolitely(byus).②Hetookawaythebox.→Theboxwastakenawaybyhim.含有賓語補(bǔ)足語的句子改為變動(dòng)語態(tài)。(賓補(bǔ)放在原來位置不變)例:①WecallhimXiaoMa.主謂賓賓補(bǔ)→HeiscalledXiaoMabyus.②Hefoundthebookveryinteresting.→Thebookwasfoundveryinterestingbyhim.【語法】C.沒有被動(dòng)語態(tài)的動(dòng)詞:在英語中,有些不及物動(dòng)詞的主動(dòng)語態(tài)可以表示被動(dòng)意義。這些不及物動(dòng)詞有:1.表示開始和結(jié)束的動(dòng)詞沒有被動(dòng)語態(tài),如:begin,start,finish,end,close等,當(dāng)主語為“事物”且不強(qiáng)調(diào)動(dòng)作的執(zhí)行者時(shí)。例如:①Themeetingwillbeginat8:00a.m.tomorrow.②Thelibraryopensat9:00a.m.andclosesat5:00p.m.2.★某些表示“發(fā)生”意義的不及物動(dòng)詞如:happen=takeplace無被動(dòng)語態(tài),如:③Manychangeshavehappenedinourhometown.(happen沒有被動(dòng)形式)3.★大多數(shù)系動(dòng)詞:feel(摸起來),sound(聽起來),look(看起來),smell(聞起來),taste(嘗起來)等詞無被動(dòng)語態(tài),它們的主動(dòng)形式表示被動(dòng)意義。例:④Theskirtfeelsverysoft.這件裙子摸起來很柔軟。(用主動(dòng)表示被動(dòng)意義)⑤Thefoodtastesdelicious.(用主動(dòng)表示被動(dòng)意義)⑥Thisideasoundsgreat.(用主動(dòng)表示被動(dòng)意義)4.某些可與well,easily等副詞連用的不及物動(dòng)詞無被動(dòng),★如:read,write,wash,sell等。例如:⑦Thisskirtwasheseasily.這件裙子很容易洗。(用主動(dòng)表示被動(dòng)意義)⑧Thepenwriteswell.這支鋼筆很好寫。(用主動(dòng)表示被動(dòng)意義)⑨Thiskindofshoessellswell.這種鞋子很好賣。(用主動(dòng)表示被動(dòng)意義)5.有些不及物動(dòng)詞或動(dòng)詞短語無被動(dòng)語態(tài):appear,die,disappear,fail,last,lie,remain,sit,spread(傳播),stand,etrue,fallasleep,...⑩Thefilmlastedfor3hours.(last沒有被動(dòng)形式)6.needdoingsth.含有被動(dòng)意義。⑾Mywatchneedsrepairing.=Mywatchneedstoberepaired.我的手表修理。★needdoing=needtobedone【語法】D.被動(dòng)語態(tài)與系表結(jié)構(gòu):1.Thedoorwasclosedlastnight.(系表結(jié)構(gòu),強(qiáng)調(diào)狀態(tài))2.ThedoorwasclosedbyTomlastnight.(被動(dòng)語態(tài),強(qiáng)調(diào)動(dòng)作)【語法】E.被動(dòng)語態(tài)與過去分詞短語作后置定語:1.ThecatiscalledMimi.2.Thereisacat(calledMimi)inthehouse.【語法】F.與被動(dòng)語態(tài)相關(guān)的一些短語:1.becoveredwith+雪、樹林等becoveredby+森林等2.bemadeof由……制成(能看出原材料)

【例句】The

pipes

shouldbe

made

of

plastic.

這些管子應(yīng)該是用塑料制作的。bemadefrom由……制成(不能看出原材料)【例句】Weallknowthatthepaperismadefromwood.我們都知道紙是由木頭制成的bemadein+年代、地點(diǎn)3.beusedas….被用來作為….

【例句】In

thepast,cloth

and

knives

can

be

usedas

money.

在過去,刀和布匹可以被當(dāng)作錢用beusedtodosth.=beusedfor(doing)sth.被用來做某事

【例句】puters

canbeused

to

do

alot

of

work

now.

如今電腦可用來做許多事。4.besurprisedby/at…對…感到驚奇【語法】G.重點(diǎn)短語句型1.Theshowwillbeheldatthetownhall.表演將在鎮(zhèn)上大禮堂被舉行。=Theshowwilltakeplaceatthetownhall.【takeplace沒有被動(dòng)】2.bethrownintolakes被扔進(jìn)湖里3.Theairisfilledwithpollution.【befilledwith被裝滿=befullof充滿】4.makepeopleill/sick使人們生病=makepeoplegetillness5.Morepeoplewillbehurtinthefutureifitisnotcleanedup.【cleanup:清理(動(dòng)副詞組)】6.Aswellaspeople,animalsareharmedbypollution.和人類一樣,動(dòng)物也受到污染的傷害?!铫賖armsb.=doharmtosb.傷害某人【harm動(dòng)詞或名詞:傷害】★②beharmfultosb.對某人是有害的【harmful形容詞:有害的】7.landandwaterpollution土地和水污染8.Ifwedonotacttoimprovetheenvironment,morelivingthingswillbekilledbypollution.★①acttodosth.=takeactiontodosth.采取行動(dòng)做某事★②livingthings活著的東西(生物)【區(qū)分】living形容詞:活著的(常作定語修飾名詞,也可作表語構(gòu)成系表結(jié)構(gòu))alive形容詞:活著的(只能作表語構(gòu)成系表結(jié)構(gòu),不能作定語修飾名詞)lively形容詞:生動(dòng)的、充滿生機(jī)的live形容詞:直播的9.Allofuswillhaveachancetothinkabouttheworldaroundus.①haveachancetodosth.有機(jī)會做某事②thinkabout考慮10.worktogether合作語法練習(xí):一、單項(xiàng)選擇1.IamafraidthatIcan’tfinishthetasksuccessfully.Don’tworry.You__________plentyoftimetodoit.A.willbegivenB.giveC.willgive2.Anewlibrary_______inourschoolnextyear.A.willbebuiltB.buildsC.isbuiltD.willbuild3.Youhavetostaybehindifyourhomework_____________beforefiveo’clock.A.isn’tdoneB.won’tbedoneC.doesn’tdoD.wasn’tdone4.Whencanwegohomethisafternoon,MrZhang?Youcan’tleaveuntilthework_____________.A.finishesB.willbefinishedC.hasfinishedD.isfinished5.Moremoney________whenweusebothsidesofpaper.A.willsaveB.wassavedC.hassavedD.willbesaved二、將下列的句子改成被動(dòng)語態(tài)1.Theywillfinishtheworkintendays._____________________________________________2.Wewillholdasportsmeetingnextweek.______________________________________________3.Childrenwilltakesomephotosintheschoolyardtomorrow._________________________________________________4.Hewillreturnthebooktothelibraryintwodays._________________________________________________5.Theheadmasterwillgiveusatalkthisafternoon._________________________________________________四、Integratedskills1.doasurveyonsth.做一個(gè)關(guān)于某事的調(diào)查2.asurveyonstudents’dailyhabits關(guān)于學(xué)生日常習(xí)慣3.turnoffthetapewhilebrushingteeth當(dāng)刷牙的時(shí)侯關(guān)掉水龍頭★①turnon/off打開/關(guān)閉(電器、水龍頭)【動(dòng)副詞組】★②turnup/down調(diào)高/調(diào)低音量【動(dòng)副詞組】4.lessthan10minutes少于10分鐘→morethan10minutes多于10分鐘5.thenumberofstudents學(xué)生的數(shù)量6.usebothsidesofthepaper用紙的兩面7.recycleemptybottles回收空瓶子8.turnoffthelights關(guān)燈9.theresult(s)ofthesurvey調(diào)查的結(jié)果10.Thesurveyshowsthatstudentsaredoingalottohelpprotecttheenvironment.這次調(diào)查表明學(xué)生們正在許多事情來幫助保護(hù)環(huán)境。11.Therearestillmanymorethings(that)theycando(定從).他們?nèi)匀挥懈嗟枚嗟氖虑榭梢宰觥?2.looknicerwithmoretreesaround周圍帶有更多的樹木看起來更加漂亮13.Airpollutionisharmfultoourhealth.空氣污染對我們的健康是有害的。14.helpkeepsoilinplaceduringstorms幫助保持土壤在暴風(fēng)雨中不流失★inplace在正確的位置=intherightplace15.reducedustandhelpkeeptheairclean減少灰塵并幫助保持空氣清潔16.providehomeforanimals給動(dòng)物提供家園五、Studyskills(一)Checkingyourwork檢查你的工作(作業(yè)、作品)錯(cuò)誤類型:Wwordusagemistake單詞用法錯(cuò)誤Ppunctuationmistake標(biāo)點(diǎn)錯(cuò)誤Sspellingmistake拼寫錯(cuò)誤Mmissingword漏詞Ggrammaticalmistake語法錯(cuò)誤(二)重點(diǎn)短語句型。1.dependonnaturalresourcestolive依靠自然資源來生存2.haveawideruseforfactories對工廠來說有更廣闊的用途3.bedugupfromtheground從地底下被挖出來4.usethemwisely明智地使用他們5.bethrownawaycarelessly被滿不在乎地扔掉【拓展:carelessness名詞:粗心】6.Coal,oilandnaturalgasbeformedoverthousandsorevenmillionsofyears.煤炭、石油和天然氣的形成需要數(shù)千年甚至數(shù)百萬年?!咀ⅰ竣賔orm作動(dòng)詞:形成【作及物動(dòng)詞時(shí)常用被動(dòng)語態(tài);做不及物動(dòng)詞時(shí)常用主動(dòng)語態(tài)表被動(dòng)】②form作名詞:形式;外表;表格7.★ifpossible=ifsb.can如果可能的話六、Task1.changefortheworse變得更加糟糕=beeworse2.It’stimeforustogogreen.是訪我們過綠色生活的時(shí)候了。★gogreen生產(chǎn)或使用綠色產(chǎn)品中考鏈接:翻譯:我們的環(huán)境正變得越來越糟糕,所以是時(shí)候環(huán)保了。3.Inordertosavepower,weshouldturnoffthelightswhenweleavearoom.為了節(jié)約電能,我們應(yīng)該在離開房間的時(shí)候關(guān)燈。4.beinuse投入使用TheYangzhou

subway

willbe

in

use.

揚(yáng)州地鐵將投入使用。5.takeourownbagswhenshopping當(dāng)購物時(shí)帶上我們自己的購物袋6.Weshouldseparatewasteintodifferentgroupssothatitcanberecycled.我們應(yīng)該將垃圾分類成不同的組別,以便于被回收利用?!緟^(qū)分】★①so....that....如此.....以致.....【that常引導(dǎo)結(jié)果狀語從句】Heissoyoungthathecan’tgotoschool.★②......sothat........以便于,為了.....【sothat常引導(dǎo)目的狀語從句】I'll

give

you

a

key

sothatyou

can

letyourself

in.

我把鑰匙給你,你可以自己開門進(jìn)去。7.developagreenlifestyle養(yǎng)成環(huán)保的生活方式8.Herearesomesimplestepstotake.這兒是一些可采用的簡單的步驟?!緎imply副詞:簡直】I

simply

adore

his

music!

我簡直太喜愛他的音樂了!9.Followthesesmallsteps,andyoucanmakeabigdifferencetotheEarth.遵循這些小步驟,你可以對地球產(chǎn)生大影響課后練習(xí)一、詞匯1.Suchanimportantproblemshouldbediscussed____________(serious).2.________(dig)aholelargeenoughforthetree.3.Hehasmadea___________(嚴(yán)重的)mistakethistime.4.It’s__________(明智的)tobringamapwithyouwhenyoudotravelling.5.Thegovernmenthastakenactionto_________(減少)theriskofheartdiseases.6.Whetherhecangoornot____________(取決于)hisparents’wishes.7.Youwillbe_________(罰款)ifyoudon’tobeytherules.8________(luck),hedidn’thurthimselftoday.9.Someoftheoldclothescan__________(sell)incharityshops.10.Therearemany________(different)betweenthem.二、單選()1.Ithinkdrinkingmilkeverymorningisgood_________ourhealth.Yes,Iagree__________you.A.to;toB.with;toC.at;withD.for;with()2.Please__________thewaterwhenyoubrushyourteeth.A.takedownB.turnupC.takeawayD.turnoff()3.Carsmakeourlifeeasier,__________,theybringenvironmentproblems.A.asB.orC.butD.with()4.Everyyeardrivingafterdrinkingwine__________alotoftrafficaccidents.A.happensB.providesC.causes()5.Samisawaiter,________hereallywantstobeasinger.A.orB.ifC.butD.because()6.She________livewithhergrandparents,butshedoesn’tnow.A.usedtoB.isusedtoC.wasusedtoD.useto()7.Youcan_________thatdress.Itlooksnice.A.turnonB.getonC.tryonD.putoff()8.Studentsareusuallyinterestedinsports.Somelikerunning,somelikeswimming,________likeballgame.A.anotherB.othersC.theotherD.other()9.ManychildreninBritain__________tohavetheirownbankcardsthesedays.A.allowB.allowedC.areallowedD.wereallowed()10.YesterdayI______allthesalttocookdumplings.Ineedtobuysomenow.A.ateupB.runoutofC.ranofD.ranoutof()11.Sir,didyouseethesign"NoParking"?Sorry.Ididn'tknowparkinghereisn't_______.A.prevented B.refusedC.allowedD.expected()12.Howdoyoulikethisone?Itisanicedigitalcamera,_______alittleexpensive.A.because B.since C.thoughD.unless()13.Thiskindoficecream_______delicious.I'msureit_______well.A.istasted;issold B.tastes;issoldC.istasted;sells D.tastes;sells()14.Thefloodwashedawaymanyvillages._______,manypeoplehavenowheretolive.A.AsaresultB.SothatC.Asaresultof D.Infact()15._______volunteersfromallovertheworldarehelpingsurvivorsrebuildtheirhomes.A.Threehundredsof B.HundredofC.Threehundreds D.Hundredsof()16.Thefactory_____itswasteintotheriver,butnowitrecyclesthewasteinanewway.A.usedtoput B.isusedtoputC.usedtoputting D.isusedtopu

溫馨提示

  • 1. 本站所有資源如無特殊說明,都需要本地電腦安裝OFFICE2007和PDF閱讀器。圖紙軟件為CAD,CAXA,PROE,UG,SolidWorks等.壓縮文件請下載最新的WinRAR軟件解壓。
  • 2. 本站的文檔不包含任何第三方提供的附件圖紙等,如果需要附件,請聯(lián)系上傳者。文件的所有權(quán)益歸上傳用戶所有。
  • 3. 本站RAR壓縮包中若帶圖紙,網(wǎng)頁內(nèi)容里面會有圖紙預(yù)覽,若沒有圖紙預(yù)覽就沒有圖紙。
  • 4. 未經(jīng)權(quán)益所有人同意不得將文件中的內(nèi)容挪作商業(yè)或盈利用途。
  • 5. 人人文庫網(wǎng)僅提供信息存儲空間,僅對用戶上傳內(nèi)容的表現(xiàn)方式做保護(hù)處理,對用戶上傳分享的文檔內(nèi)容本身不做任何修改或編輯,并不能對任何下載內(nèi)容負(fù)責(zé)。
  • 6. 下載文件中如有侵權(quán)或不適當(dāng)內(nèi)容,請與我們聯(lián)系,我們立即糾正。
  • 7. 本站不保證下載資源的準(zhǔn)確性、安全性和完整性, 同時(shí)也不承擔(dān)用戶因使用這些下載資源對自己和他人造成任何形式的傷害或損失。

評論

0/150

提交評論