最新大学英语四级考试全真模拟试题五和答案

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1、最新大学英语四级考试全真模拟试题五和答案“Growingpopulationswillworsenproblemswithwater,”saysPeterH.Gleick,anenvironmentalscientistatthePacificInstituteforstudiesinDevelopment,Environment,andSecurity,aresearchorganizationinCalifornia.Hefearsthatbytheyear2025,asmanyasonethirdo

2、ftheworld’sprojected8.3billionpeoplewillsufferfromwatershortages.WhereWaterGoesOnly2.5percentofallwateronEarthisfreshwater,watersuitablefordrinkingandgrowingfood,saysSandraPostel,directoroftheGlobalWaterPolicyProjectinAmherst,Mass.Twothirdsofthisfreshwate

3、rislockedinglaciersandicecaps.Infact,onlyatinypercentageoffreshwaterispartofthewatercycle,inwhichwaterevaporatesandrisesintotheatmosphere,thencondensesandfallsbacktoEarthasprecipitation（rainorsnow）.Someprecipitationrunsofflandtolakesandoceans,andsomebecome

4、sgroundwater,waterthatseepsintotheearth.MuchofthisrenewablefreshwaterendsupinremoteplacesliketheAmazonriverbasininBrazil,wherefewpeoplelive.Infact,theworld’spopulationhasaccesstoonly12,500cubickilometersoffreshwater—abouttheamountofwaterinLakeSuperior.Andp

5、eopleusehalfofthisamountalready.“Ifwaterdemandcontinuestoclimbrapidly,”saysPostel,“therewillbesevereshortagesanddamagetotheaquaticenvironment.”ClosetoHomeWaterwoesmayseemremotetopeoplelivinginrichcountriesliketheUnitedStates.ButAmericanscouldfaceseriouswat

6、ershortages,tooespeciallyinareasthatrelyongroundwater.Groundwateraccumulatesinaquifers,layersofsandandgravelthatliebetweensoilandbedrock.（Foreveryliterofsurfacewater,morethan90litersarehiddenunderground）.AlthoughtheUnitedStateshaslargeaquifers,farmers,ranc

7、hers,andcitiesaretappingmanyofthemforwaterfasterthannaturecanreplenishit.InnorthwestTexas,forexample,overpumpinghasshrunkgroundwatersuppliesby25percent,accordingtoPostel.Americansmayfaceevenmoreurgentproblemsfrompollution.DrinkingwaterintheUnitedStatesisge

8、nerallysafeandmeetshighstandards.Nevertheless,oneinfiveAmericanseverydayunknowinglydrinkstapwatercontaminatedwithbacteriaandchemicalwastes,accordingtotheEnvironmentalProtectionAgency.InMilwaukee,400,000people