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thirdoftheworld’sprojected8

2、.3billionpeoplewillsufferfromwatershortages.WhereWaterGoesOnly2.5percentofallwateronEarthisfreshwater,watersuitablefordrinkingandgrowingfood,saysSandraPostel,directoroftheGlobalWaterPolicyProjectinAmherst,Mass.Twothirdsofthisfreshwaterislockedinglaciersandicecaps.Infact,onlya

3、tinypercentageoffreshwaterispartofthewatercycle,inwhichwaterevaporatesandrisesintotheatmosphere,thencondensesandfallsbacktoEarthasprecipitation（rainorsnow）.Someprecipitationrunsofflandtolakesandoceans,andsomebecomesgroundwater,waterthatseepsintotheearth.Muchofthisrenewablefres

4、hwaterendsupinremoteplacesliketheAmazonriverbasininBrazil,wherefewpeoplelive.Infact,theworld’spopulationhasaccesstoonly12,500cubickilometersoffreshwater—abouttheamountofwaterinLakeSuperior.Andpeopleusehalfofthisamountalready.“Ifwaterdemandcontinuestoclimbrapidly,”saysPostel,“t

5、herewillbesevereshortagesanddamagetotheaquaticenvironment.”ClosetoHomeWaterwoesmayseemremotetopeoplelivinginrichcountriesliketheUnitedStates.ButAmericanscouldfaceseriouswatershortages,tooespeciallyinareasthatrelyongroundwater.Groundwateraccumulatesinaquifers,layersofsandandgra

6、velthatliebetweensoilandbedrock.（Foreveryliterofsurfacewater,morethan90litersarehiddenunderground）.AlthoughtheUnitedStateshaslargeaquifers,farmers,ranchers,andcitiesaretappingmanyofthemforwaterfasterthannaturecanreplenishit.InnorthwestTexas,forexample,overpumpinghasshrunkgroun

7、dwatersuppliesby25percent,accordingtoPostel.Americansmayfaceevenmoreurgentproblemsfrompollution.DrinkingwaterintheUnitedStatesisgenerallysafeandmeetshighstandards.Nevertheless,oneinfiveAmericanseverydayunknowinglydrinkstapwatercontaminatedwithbacteriaandchemicalwastes,accordin

8、gtotheEnvironmentalProtectionAgency.InMilwaukee,400,000people