（新课标）2020高考英语二轮总复习 第三讲 阅读理解 3.7 主旨大意（一）段落主旨课件

第三讲阅读理解第七节主旨大意(一)段落主旨母题探究栏目导航题组集训限时训练(2019·高考浙江卷)Californiahaslosthalfitsbigtreessincethe1930s,accordingtoastudytobepublishedTuesdayandclimatechangeseemstobeamajorfactor(因素)．Thenumberoftreeslargerthantwofeetacrosshasdeclinedby50percentonmorethan46,000squaremilesofCaliforniaforests,thenewstudyfinds.Noareawassparedorunaffected,fromthefoggynortherncoasttotheSierraNevadaMountainstotheSanGabrielsaboveLosAngeles.IntheSierrahighcountry,thenumberofbigtreeshasfallenbymorethan55percent;inpartsofsouthernCaliforniathedeclinewasnearly75percent.Manyfactorscontributedtothedecline,saidPatrickMclntyre,anecologistwhowastheleadauthorofthestudy.Woodcutterstargetedbigtrees.Housingdevelopmentpushedintothewoods.AggressivewildfirecontrolhasleftCaliforniaforestscrowdedwithsmalltreesthatcompetewithbigtreesforresources(资源)．ButincomparingastudyofCaliforniaforestsdoneinthe1920sand1930swithanotheronebetween2001and2010,McIntyreandhiscolleaguesdocumentedawidespreaddeathofbigtreesthatwasevidenteveninwildlandsprotectedfromwoodcuttingordevelopment.Thelossofbigtreeswasgreatestinareaswheretreeshadsufferedthegreatestwatershortage.Theresearchersfiguredoutwaterstresswithacomputermodelthatcalculatedhowmuchwatertreesweregettingincomparisonwithhowmuchtheyneeded,takingintoaccountsuchthingsasrainfall,airtemperature,dampnessofsoil,andthetimingofsnowmelt(融雪)．Sincethe1930s,McIntyresaid,thebiggestfactorsdrivingupwaterstressinthestatehavebeenrisingtemperatures,whichcausetreestolosemorewatertotheair,andearliersnowmelt,whichreducesthewatersupplyavailabletotreesduringthedryseason.27．Whatisthesecondparagraphmainlyabout?A．Theseriousnessofbig­treelossinCalifornia.B.TheincreasingvarietyofCaliforniabigtrees.C．ThedistributionofbigtreesinCaliforniaforests.D.TheinfluenceoffarmingonbigtreesinCalifornia.27．段落大意题。根据第二段中提到的数字可知，该段主要描述了加州森林大树急剧减少的严重性。答案：A[语篇解读]本文是议论文。文章主要讲述了美国加利福尼亚州的森林中大树急剧减少的现象，并分析了原因。[长难句分析]Theresearchersfiguredoutwaterstresswithacomputermodelthatcalculatedhowmuchwatertreesweregettingincomparisonwithhowmuchtheyneeded,takingintoaccountsuchthingsasrainfall,airtemperature,dampnessofsoil,andthetimingofsnowmelt(融雪)．(第五段第二句)句意：研究人员用一个计算机模型计算出了水分胁迫，该模型计算出了树木所需的水量，同时考虑到了降雨、气温、土壤湿、融雪时间等因素。[分析]这是一个主从复合句。句中that引导的是一个定语从句修饰名词acomputermodel；howmuch引导宾语从句，从句中含有一个现在分词短语作状语。【方法点津】段落主旨题是针对某一段或几段的主题提问。主题句可能是段落的首句、末句，也可能需要从上下文中寻找或总结。概括段落主旨的方法是：先看段首和段尾有没有主题句，如果有主题句，那么主题句加工之后就是本段的中心；若无明显主题句，就需要通过关键句来概括。所以对于说明文和论述文，段落主旨重点在于所在段落的中心句。而如果是记叙文，就需要通读整段文字后自己归纳。比如本题中的第二段没有明显的主题句，要靠考生通读本段然后总结出段落大意。通常情况下，干扰项具有如下五个特点：1．主题变大。干扰项所归纳、概括的范围变大，超过实际所提及的内容。2．断章取义。干扰项常以文章中的个别信息或个别字眼作为选项的设计内容，或者以次要的事实或细节充当全文的主要观点。3．以偏概全。干扰项只表述了文章的部分内容，也就是文章的局部信息。4．无中生有，似是而非。有的干扰项中的关键词语好似在文章中谈到了，但认真分析之后会发现这类干扰项的内容与文章的内容毫无联系。5．张冠李戴。命题者有意地把属于A的特征放在B的身上，构成一个干扰项。我们在不注意的情况下，会错选答案。A2019·河北省衡水中学全国高三统一联考AlmosteverysecondofeverydayanolderadultfallsintheUnitedStates.That'sapproximately29millionfallsperyearandnearly27,000deathsaccordingtotheCentersforDiseaseControlandPrevention.Stillinthestatingstage,theActivePelvisOrthosis(APO)systeminSwitzerlandwantstomakealightweight,wearableexoskeleton(外骨骼)thatcoulddetectsignsofbalancelossandassistwithbalancerecoverytokeeptheelderlywearerfromfalling,onlywhenneeded.Otherexoskeletons,eitherindevelopmentoronthemarkettoday,assistwithmovementandmakeheavyobjectsfeellighter.Mobility­impairedpeoplecanwalkagain.Butnoneofthesedevicespredictwhatthewearerisgoingtodonextandtakemeasurestocorrectanunsteadymove.The3kilogram(6.7pound)exoskeletonwasbuiltentirelyfromscratchbytheresearchteamandisdesignedtobewornonthelowerhalfofthebody.Awaistbandconnectstotwomovablecarbonfiberbraces(支架),eachonepositionedontheoutersideofaleg.Tinymotorsandso­called“adaptiveoscillators”(适配振荡器)inthecomputercircuitsuseaspecialprocesstodetectthewearer'suniquepaces.Thatparttakesjustafewminutes.Whilewearingtheexoskeleton,apersonmayfeelthebracesandthemotorspushingslightlyontheirlegs.Iftheirpacesgoagainstnormal,themotorscreateaforceinthebracesthatcausethemtostiffenupandpushalittlemorestronglyagainstthelegs,whichprovidesstability.Inthenextthreeyears,theAPOhopestodevelopsomethingthatiscommerciallyavailable.1．Whyisthenewexoskeletoninvented?A．Toslowerusers'walkingpaces.B．Toimproveusers'walkingabilityC．Topromoteusers'senseofbalance.D．Topreventusersfromfalling.1．D解析：细节理解题。根据第二段第一句中“alightweight,wearableexoskeleton(外骨骼)thatcoulddetectsignsofbalancelossandassistwithbalancerecoverytokeeptheelderlywearerfromfalling…”可知，发明这套外骨骼装置的目的就是防止使用者摔倒，故选D。[语篇解读]本文是一篇科技说明文。文章主要介绍了一款新的可以防止穿戴者摔倒的外骨骼装置，这种外骨骼装置可以预知穿戴者的行动并采取措施纠正他们不稳定的移动。2．What'sthefeatureofthenewexoskeleton?A．Itkeepsuserswarm.B．Itiswornontheback.C．Ithelpsusersmovearound.D．Itcorrectsanunsteadymove.2．D解析：细节理解题。根据第三段最后一句“Butnoneofthesedevicespredictwhatthewearerisgoingtodonextandtakemeasurestocorrectanunsteadymove.”可知，这款新型的外骨骼装置的特点是可以纠正不稳定的移动，故选D。3．WhatdoesParagraph4mainlytalkabout?A．Howthenewexoskeletonworks.B．Wherethebracesarepositioned.C．Howlongittakestodetecttheuser'spaces.D．Whatthenewexoskeletonwasbuiltfrom.3．A解析：段落大意题。综合文章第四段内容可知，本段主要讲述了这种新的外骨骼装置的工作原理，故选A。4．Whatisthepurposeoftheauthorinwr