小编为备考的同学们整理了19年四级读练习题，希望可以为大家带来帮助，预祝大家高分通过。

AgricultureisthenumberoneindustryintheUnitedStatesandagriculturalproductsarethecountry'sleadingexport.AmericanfarmersmanagetofeednotonlythetotalpopulationoftheUnitedStates,butalsomillionsofotherpeoplethroughouttherestoftheworld.Cornandsoybeanexportsaloneaccountforapproximately75percentoftheamountsoldinworldmarkets.Thisproductivity,however,hasitsprice.Intensivecultivationexposestheearthtothedamagingforcesofnature.Everyyearwindandwaterremovetonsofrichsoilfromthenation'scroplands.Eachfieldiscoveredbyalimitedamountoftopsoil,theupperlayerofearthwhichisrichestinthenutrientsandmineralsnecessaryforgrowingcrops.EversincethefirstfarmersarrivedintheMidwestalmost200yearsago，cultivationand,consequently,erosionhavebeendecreasingthesupplyoftopsoil.Inthe1830s,nearlytwofeetofrich,blacktopsoilcoveredtheMidwest.Todaytheaveragedepthisonlyeightinches,andeverydecadeanotherinchisblownorwashedaway.Thiserosionissteadilydecreasingtheproductivityofvaluablecropland.AUnitedStatesAgriculturalDepartmentsurveystatesthatiferosioncontinuesatitspresentrate,cornandsoybeanyieldsintheMidwestmaydropasmuchas30percentoverthenext50years.Sofar,farmershavebeenabletocompensateforthelossoffertiletopsoilbyapplyingmorechemicalfertilizerstotheirfields;however,whilethispracticehasincreasedcropyields,ithasbeendevastatingforecology.Agriculturehasbecomeoneofthebiggestpollutersofthenation'spreciouswatersupply.Rivers,lakes,andundergroundreservesofwaterarebeingfilledinandpoisonedbysoilandchemicalscarriedbydrainagefromerodingfields.Furthermore,fertilizersonlyreplenishthesoilstheydonotpreventitsloss.

26.Thelastsentenceinthefirstparagraphgivesanexampletoshow_______.

A.thatAmericanfarmersmanagetofeedthetotalpopulationoftheU.S.B.theleadingpositionoftheU.S.farmingintheworldC.howimportantAmericanpeopleconsidertheirfarmingD.thatmanypeopleintheworldrelyontheexportoftheagriculturalproductsoftheU.S.A.

27.Inordertocompensateforthelossoffertiletopsoil,farmershavebeen_______.

A.plantinglesscornandsoybeanB.puttingfertilizersontheirfieldsC.preventingsoilerosionD.decreasingthesupplyoftopsoil

28.Atthepresentrate,approximatelyhowmanyyearslatertheblacktopsoilnowcoveringtheMidwestwillcompletelybeblownorwashedaway?

A.120yearslater..B.80yearslater.C.50yearslater.D.100yearslater.

29."Thispractice"inParagraph4refersto_______.

A.thatfarmershaveloweredtheyieldofcornandsoybeanB.thatfarmershaveexpandedcroplandsC.thatfarmershaveappliedmorechemicalfertilizersD.thatthetopsoilhasbeendecreasedgreatly

30.AllofthefollowingarestatementsaboutthedisadvantagesoffertilizersEXCEPTthat

A.theyreplenishthesoilB.theydonotpreventthelossofsoilC.theyaredestroyingtheecologyD.theypollutethenation'swatersupply

答案：26.D27.B28.B29.C30.A