职称英语考试卫生A级阅读理解真题预测
职称英语考试卫生A级阅读理解真题预测1
第4部分：阅读理解(第31——45题，每题3分，共45分)
下面有3篇短文，每篇短文后有5道题。请根据短文内容，为每题确定1个最佳选项。
第二篇DeforestationandDesertification(沙漠化)
TheSahelzoneliesbetweentheSaharadesertandthefertilesavannahs(热带大草原)ofnorthernNigeriaandSouthSudan.ThewordsahelcomesfromArabicandmeansmarginalortransitional,andthisisagooddescriptionofthesesemi-arid(半干旱)lands,whichoccupymuchoftheWesternAfricancountriesofMail,Mauritania,Niger,andChad.
Unfortunately,overthelastcenturytheSaharadeserthassteadilycreptsouthwardseatingintoonceproductiveSahellands.UnitedNationssurveysshowthatover70percentofthedrylandinagricultureuseinAfricahasdeterioratedoverthelast30years.Droughtshavebecomemoresevere,themostrecentlastingovertwentyyearsinpartsoftheSahelregion.ThesameprocessofdesertificationistakingplaceacrosssouthernAfricaastheKalaharidesertadvancesintoBotswanaandpartsofSouthAfrica
Oneofthemajorcausesofthisdesertadvanceispooragriculturallanduse,drivenbythepressuresofincreasingpopulation.Overgrazing一keepingtoomanyfarmanimalsontheland一meansthatgrassesandotherplantscannotrecover,andscarcewatersuppliesareexhausted.Overcultivation一tryingtogrowtoomanycropsonpoorland一resultsinthesoilbecomingevenlessfertileanddrier,andbeginningtobreakup.Soilerosion(侵蚀)follows,andthelandturnsintodesert.
Anothercauseofdesertificationislossoftreecover.Treesarecutdownforuseasfuelandtoclearlandforagriculturaluse.Treerootshelptobindthesoiltogether,toconservemoisture,andtoprovideahabitatforotherplantsandanimals.Whentreesarecutdown,thesoilbeginstodryandloosen,windandrainerosionincrease,otherplantspeciesdie,andeventuallythefertiletopsoilmaybealmostentirelylost,leavingonlybarerockanddust.
Theeffectsoflossoftopsoilandincreaseddrought