大学英语四级考试全真预测试卷

VOA英语网（30minutes）Directions:Forthispart,youareallowed30minutestowriteacompositiononthetopicChoosinganOccupation.Youshouldwriteatleast120wordsfollowingtheoutlinegivenbelowinChinese:1.选择职业是一个人要面对的众多难题之一。2.需要花时间去选择职业。3.选择职业时可以向多人寻求建议和帮助。PartIIReadingComprehension(SkimmingandScanning)(15minutes)Directions:Inthispart,youwillhave15minutestogooverthepassagequicklyandanswerthequestionsonAnswerSheet1.Forquestions1-7,markY(forYES)ifthestatementagreeswiththeinformationgiveninthepassage;N(forNO)ifthestatementcontradictstheinformationgiveninthepassage;NG(forNOTGIVEN)iftheinformationisnotgiveninthepassage.Forquestions8-10,completethesentenceswiththeinformationgiveninthepassage.WillWeRunOutofWater?Picturea“ghostship”sinkingintothesand,lefttorotondrylandbyarecedingsea.Thenimagineduststormssweepinguptoxicpesticidesandchemicalfertilizersfromthedryseabedandspewingthemacrosstownsandvillages.Seemlikeascenefromamovieabouttheendoftheworld?ForpeoplelivingneartheAralSeainCentralAsia,it’salltooreal.Thirtyyearsago,governmentplannersdivertedtheriversthatflowintotheseainordertoirrigate（providewaterfor）farmland.Asaresult,theseahasshrunktohalfitsoriginalsize,strandingshipsondryland.Theseawaterhastripledinsaltcontentandbecomepolluted,killingall24nativespeciesoffish.Similarlarge-scaleeffortstoredirectwaterinotherpartsoftheworldhavealsoendedinecologicalcrisis,accordingtonumerousenvironmentalgroups.Butmanycountriescontinuetobuildmassivedamsandirrigationsystems,eventhoughsuchprojectscancreatemoreproblemsthantheyfix.Why?Peopleinmanypartsoftheworldaredesperateforwater,andmorepeoplewillneedmorewaterinthenextcentury.“Growingpopulationswillworsenproblemswithwater,”saysPeterH.Gleick,anenvironmentalscientistatthePacificInstituteforstudiesinDevelopment,Environment,andSecurity,aresearchorganizationinCalifornia.Hefearsthatbytheyear2025,asmanyasonethirdoftheworld’sprojected8.3billionpeoplewillsufferfromwatershortages.WhereWaterGoesOnly2.5percentofallwateronEarthisfreshwater,watersuitablefordrinkingandgrowingfood,saysSandraPostel,directoroftheGlobalWaterPolicyProjectinAmherst,Mass.Twothirdsofthisfreshwaterislockedinglaciersandicecaps.Infact,onlyatinypercentageoffreshwaterispartofthewatercycle,inwhichwaterevaporatesandrisesintotheatmosphere,thencondensesandfallsbacktoEarthasprecipitation（rainorsnow）.VOA英语网’spopulationhasaccesstoonly12,500cubickilometersoffreshwater—abouttheamountofwaterinLakeSuperior.Andpeopleusehalfofthisamountalready.“Ifwaterdemandcontinuestoclimbrapidly,”saysPostel,“therewillbesevereshortagesanddamagetotheaquaticenvironment.”ClosetoHomeWaterwoesmayseemremotetopeoplelivinginrichcountriesliketheUnitedStates.ButAmericanscouldfaceseriouswatershortages,tooespeciallyinareasthatrelyongroundwater.Groundwateraccumulatesinaquifers,layersofsandandgravelthatliebetweensoilandbedrock.（Foreveryliterofsurfacewater,morethan90litersarehiddenunderground.）AlthoughtheUnitedStateshaslargeaquifers,farmers,ranchers,andcitiesaretappingmanyofthemforwaterfasterthannaturecanreplenishit.InnorthwestTexas,forexample,overpumpinghasshrunkgroundwatersuppliesby25percent,accordingtoPostel.Americansmayfaceevenmoreurgentproblemsfrompollution.DrinkingwaterintheUnitedStatesisgenerallysafeandmeetshighstandards.Nevertheless,oneinfiveAmericanseverydayunknowinglydrinkstapwatercontaminatedwithbacteriaandchemicalwastes,accordingtotheEnvironmentalProtectionAgency.InMilwaukee,400,000peoplefellillin1993afterdrinkingtapwatertaintedwithcryptosporidium,amicrobethatcausesfever,diarrheaandvomiting.TheSourceWheredocontaminantscomefrom?Indevelopingcountries,peopledumprawsewageintothesamestreamsandriversfromwhichtheydrawwaterfordrinkingandcooking;about250millionpeopleayeargetsickfromwaterbornediseases.Indevelopedcountries,manufacturersuse100,000chemicalcompoundstomakeawiderangeofproducts.Toxicchemicalspollutewaterwhenreleaseduntreatedintoriversandlakes.(Certaincompounds,suchaspolychlorinatedbiphenyls,orPCBs,havebeenbannedintheUnitedStates.）Butalmosteveryonecontributestowaterpollution.Peopleoftenpourhouseholdcleaners,carantifreeze,andpaintthinnersdownthedrain;allofthesecontainhazardouschemicals.ScientistsstudyingwaterintheSanFranciscoBayreportedin1996that70percentofthepollutantscouldbetracedtohouseholdwaste.Farmershavebeencriticizedforoverusingherbicidesandpesticides,chemicalsthatkillweedsandinsectsbutthatpollutewateraswell.Farmersalsousenitrates,nitrogen-richfertilizerthathelpplantsgrowbutthatcanwreakhavocontheenvironment.Nitratesaresweptawaybysurfacerunofftolakesandseas.Toomanynitrates“overenrich”thesebodiesofwater,encouragingthebuildupofalgae,ormicroscopicplantsthatliveonthesurfaceofthewater.Algaedeprivethewaterofoxygenthatfishneedtosurvive,attimeschokingofflifeinanentirebodyofwater.What’stheSolution?WaterexpertG