2012届高考英语精选备考题库系列（含详解）：阅读理解（2）

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1、2012届高考英语二轮复习精选备考题库系列（含详解）：阅读理解（二）备战2012高考，精选阅读200篇，适合高三上学期使用，希望对大家有帮助。（2011年8月）Haveyouevernoticedthecolourofthewaterinariverorstreamafteraheavyrainfall?Whatdoyouthinkcausedthischangeincolour?Itissoilthathasbeenwashedintotheriverfromtheriverbankorfromthenearbyfields.Co

2、mponentsofSoilSoilismadeupofanumberoflayers(层),eachhavingitsowndistinctivecolourandtexture.Theupperlayerisknownasthelitter.Itactslikeablanket，limitingtemperaturechangesandreducingwaterloss.Thetopsoillayerismadeupofsmallparticlesofrockmixedwithrottenplantandanimalmatter

3、calledhumus(腐殖质),whichisblackandgivesthetopsoilitsdarkcolour.Thislayerisusuallyrichinnutrients,oxygen,andwater.Belowthetopsoilisthesubsoil,alayerthatcontainsmorestonesmixedwithonlysmallamountsoforganicmatter.Thislayerislighterincolourbecauseofthelackofhumus.Beneaththes

4、oilliesalayerofbedrock.Soilformsfromthebottomup.Overtimebedrockisattackedbyrain,wind,frost,andsnow.Itisgraduallybrokendownintosmallerparticlesinaprocesscalledweathering.Plantsbegintogrow，androttenmaterialsenrichthetopsoil.MostofthesoilinEasternCanada，forexample，wasform

5、edfromweatheredrockthatwasexposedwhentheicedisappeared12,000yearsago.WaterBeneaththeSoilSurfacewatercollectsandflowsabovethegroundinlakes，ponds,andrivers.Onceinthesoilorrock,itiscalledgroundwater.Gravitypullsgroundwaterthroughthesoilinaprocesscalledpercolation(渗透).Even

6、tuallythewaterreachesalayercalledthewatertable.Underthisisbedrockthroughwhichwatercannotpercolate.Aswaterpercolatesdownward,itdissolvesorganicmatterandmineralsfromthesoilandcarriesthemtodeeperlayers.Thiscausesaseriousproblembecauseplantsrequirethesenutrientsforgrowth.S

7、oilpHSoilcanbeacidic,neutral,orbasic.ThepHofthesoilisdeterminedbythenatureoftherockfromwhichitwasformed，andbythenatureoftheplantsthatgrowandrotinit.TheacidityofrainandsnowcanlowerthepHofthegroundwaterthatentersthesoil.Byburningfossilfuelssuchascoal，oilandgasoline，human

8、shavebeencontributingtohigherlevelsofacidityinmanysoils.Whenfossilfuelsareburned，gasesarereleasedintotheairandthenfal