2018年6月英语四级阅读200篇第51篇：大海中的含盐量思维导图
If the salinity(含盐量) of ocean waters is analyzed, it is found to vary only slightly from place to place.Nevertheless, some of these small changes are important. There are three
树图思维导图提供 2018年6月英语四级阅读200篇第51篇：大海中的含盐量 在线思维导图免费制作，点击“编辑”按钮，可对 2018年6月英语四级阅读200篇第51篇：大海中的含盐量 进行在线思维导图编辑，本思维导图属于思维导图模板主题，文件编号是：6b7c045b1567762604917bb6076ece60
思维导图大纲
2018年6月英语四级阅读200篇第51篇：大海中的含盐量思维导图模板大纲
Ifthesalinity(含盐量)ofoceanwatersisanalyzed,itisfoundtovaryonlyslightlyfromplacetoplace.Nevertheless,someofthesesmallchangesareimportant.Therearethreebasicprocessesthatcauseachangeinoceanicsalinity.Oneoftheseisthesubtractionofwaterfromtheoceanbymeansofevaporation--conversionofliquidwatertowatervapor.Inthismanner,thesalinityisincreased,sincethesaltsstaybehind.Ifthisiscarriedtotheextreme,ofcourse,whitecrystalsofsaltwouldbeleftbehind.
Theoppositeofevaporationisprecipitation(降水),suchasrain,bywhichwaterisaddedtotheocean.Heretheoceanisbeingdiluted(稀释)sothatthesalinityisdecreased.Thismayoccurinareasofhighrainfallorincoastalregionswhereriversflowintotheocean.Thussalinitymaybeincreasedbythesubtractionofwaterbyevaporation,ordecreasedbytheadditionoffreshwaterbyprecipitationorrunoff(形成地表水部分的降水).
Normally,intropicalregionswherethesunisverystrong,theoceansalinityissomewhathigherthanitisinotherpartsoftheworldwherethereisnotasmuchevaporation.Similarly,incoastalregionswhereriversdilutethesea,salinityissomewhatlowerthaninotheroceanicareas.
Athirdprocessbywhichsalinitymaybealteredisassociatedwiththeformationandmeltingofseaice.Whenseawaterisfrozen,thedissolvedmaterialsareleftbehind.Inthismanner,seawaterdirectlybeneathfreshlyformedseaicehasahighersalinitythanitdidbeforetheiceappeared.Ofcourse,whenthisicemelts,itwilltendtodecreasethesalinityofthesurroundingwater.
IntheWeddellSea,offAntarctica,thedensestwaterintheoceansisformedasaresultofthisfreezingprocess,whichincreasesthesalinityofcoldwater.Thisheavywatersinksandisfoundinthedeeperportionsoftheoceansoftheworld.
练习题：
Choosecorrectanswerstothequestion:
1.Thebesttitleofthepassagecanbe“_____”.
A.TypicalOceansandTheirRespectiveFeatures
B.TheCausesoftheChangesinSalinityofOceanWater
C.DifferentOceansHaveDifferentSalinity
D.ThePrecipitationandEvaporationofOceans
2.Whichofthefollowingprocesseswillincreasesalinityofoceanwaters?
A.Evaporation.
B.Precipitation.
C.Melting.
D.Dilution.
3.Accordingtothispassage,thesea_islikelytohavethelowestsalinity.
A.intropicalareas
B.offAntarctica
C.ofhighrainfall
D.withabundant
4.TheWeddellSea_____.
A.isagoodexampleofincreasedsalinityinfreezingseawater
B.ismuchlargerinareathantheArcticoceans
C.hasamuchlowersalinitynowthanever
D.hasthedenserwaterinitsupperparts
5.Coastalregionsarementionedascaseswhere_____.
A.seawaterislesssaltybecausefreshwaterjoinsin
B.riverscarryindustrialexhaustintosea
C.seaicetendstomeltmorequicklythaninthecenterofoceans
D.heavywatersinkstothedeeperportionsoftheoceans
1.[B]主旨大意题。本文第1段第3句是全文的主题句，告诉读者有三种原因致使海洋盐分变化并逐一介绍这三种原因，选项B比较全面地归纳了本文的主题。选项A和C中心词为oceans,不妥，选项D只提及了前面两种原因，不全面。
2.[A]亊实细节题。只要明白第1段第5句中的inthismanner是指第4句中的evaporation,不难做出正确选择。选项B、C会使含盐量减少,很容易排除。具体的反证分别出现在第2段首句、第3段尾句和第4段首句。
3.[C]推理判断题。综合3种情况，造成海洋含盐量低的原因有：降雨多、日晒少、远离热带和海冰融化，由此可推断选项C最符合。A和D是使海水含盐量增加的，因此可排除。B是否一定海水含盐低，文中并未提到。
4.[A]推理判断题。选项A是对最后一段第1句的同义改写。同一句可知选项C错。选项B根本没有提及。文章最后一句表明D正好与亊实相反。
5.[A]推理判断题。coastalregions字眼在文章中提到两遍，分别在第2段第3句及第3段最后一句。只要能够迅速査找到任何一处均可做出正确判断为A。B和C无原文支持;D张冠李戴，原文提及D内容涉及的是WeddellSea,而非coastalregions。
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