Trees should only be pruned when there is a good and clear reason for doing so and,fortunately, the

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【单选题】Treesshouldonlybeprunedwhenthereisagoodandclearreasonfordoingsoand,fortunately,thenumberofsuchreasonsissmall.Pruninginvolvesthecuttingawayofovergrownandunwantedbranches,andtheinexperiencedgardenercanbeencouragedbythethoughtthatmoredamageresultsfromdoingitunnecessarilythanfromleavingthetreetogrowinitsownway.First,pruningmaybedonetomakesurethattreeshaveadesiredshapeorsize.Theobjectmaybetogetatreeoftherightheight,andatthesametimetohelpthegrowthofsmallsidebrancheswhichwillthickenitsappearanceorgiveitaspecialshape.Secondly,pruningmaybedonetomakethetreehealthier.Youmaycutdiseasedordeadwood,orbranchesthatarerubbingagainsteachotherandthuscausewounds.Thehealthofatreemaybeencouragedbyremovingbranchesthatareblockingupthecentreandsopreventingthefreemovementofair.Oneresultofpruningisthatanopenwoundisleftonthetreeandthisprovidesaneasyentryfordisease,butitisawoundthatwillheal.Oftenthereisaracebetweenthehealingandthediseaseastowhetherthetreewillliveordie,sothatthereisaperiodwhenthetreeisatrisk.Itshouldbetheaimofeverygardenertoreducewhichhasbeenprunedsmoothandclean,forhealingwillbesloweddownbyroughness.Youshouldallowthecutsurfacetodryforafewhurtsandthenpaintitwithoneofthesubstancesavailablefromgardenshopsproducedespeciallyforthispurpose.Pruningisusuallywithoutinterferencefromtheleavesandalsoitisveryunlikelythatthecutsyoumakewillbleed.Ifthisdoeshappen,itis,ofcourse,impossibletopaintthemproperly.?Whatwastheauthor'spurposewhenwritingthispassage?

A、Togivepracticalinstructionforpruningatree.
B、Togiveageneraldescriptionofpruning.
C、Toexplainhowtreesdevelopdiseases.
D、Todiscussdifferentmethodsofpruning.

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