大学英语四级阅读理解试题（卷）与答案解析.

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1、大学英语四级阅读理解试题及答案（四）十六Treesshouldonlybeprunedwhenthereisagoodandclearreasonfordoingsoand,fortunately,thenumberofsuchreasonsissmall.Pruninginvolvesthecuttingawayofobergrownandunwantedbranches,andtheinexperiencedgardenercanbeencouragedbythethoughtthatmoredamageresultsfromdoingitunnecessarilyt

2、hanfromleavingthetreetogrowinitsownway.First,pruningmaybedonetomakesurethattreeshaveadesiredshapeorsize.Theobjectmaybetogetatreeoftherightheight,andatthesametimetohelpthegrowthofsmallsidebrancheswhichwillthickenitsappearanceorgiveitaspecialshape.Secondly,pruningmaybedonetomakethetreehealt

3、hier.Youmaycutdiseaedordeadwood,orbranchesthatarerubbingagainsteachotherandthuscausewounds.Thehealthofatreemaybeencouragedbyremovingbranchesthatareblockingupthecentreandsopreventingthefreemovementofair.Oneresultofpruningisthatanopenwoundisleftonthetreeandthisprovidesaneasyentryfordisease,

4、butitisawoundthatwillheal.Oftenthereisaracebetweenthehealingandthedeseaseastowhetherthetreewillliveordie,sothatthereisaperiodwhenthetreeisatrisk.Itshouldbetheaimofeverygardenertoreducewhichhasbeenprunedsmoothandclean,forhealingwillbesloweddownbyroughness.Youshouldallowthecutsurfacetodryfo

5、rafewhursandthenpaintitwithoneofthesubstancesavailablefromgardenshopsproducedespeciallyforthispurpose.Pruningisusuallywithoutinterferencefromtheleavesandalsoitisveryunlikelythatthecutsyumakewillbleed.Ifthisdoeshappen,itis,ofcourse,impossibletopaintthemproperly.1.Pruningshouldbedoneto_____

6、_.a.makethetreegrowtallerb.improvetheshapeofthetreec.getridofthesmallbranchesd.makethesmallbranchesthicker2.Treesbecomeunhealthyifthegardener______.a.allowstoomanybranchestogrowinthemiddleb.doesnotprotectthemfromwindc.forcesthemtogrowtooquicklyd.damagessomeofthesmallsidebranches3.Whyisasp

7、ecialsubstancepaintedonthetree?a.Tomakeawoundsmoothb.Topreventdiseaseenteringawoundc.Tocoveraroughsurfaced.Tohelpawoundtodry4.Agoodgardenerprunesatree______.a.atintervalsthroughouttheyearb.asquicklyaspossiblec.occasionallywhennecessaryd.regulareverywinter5.Whatwasth