Treesshouldonlybeprunedwhenthereisagoodandclearreasonfordoingsoand, fortunately,thenumberofsuchreasonsissmall.Pruninginvolvesthecuttingawayofovergrownandunwantedbranches,andtheinexperiencedgardenercanbeencouragedbythethoughtthatmoredamageresultsfromdoingitunnecessarilythanfromleavingthetreetogrowinitsownway. First,pruningmaybedonetomakesurethattreeshaveadesiredshapeorsize.Theobjectmaybetogetatreeoftherightheight,andatthesametimetohelpthegrowthofsmallsidebrancheswhichwillthickenitsappearanceorgiveitaspecialshape.Secondly,pruningmaybedonetomakethetreehealthier.Youmaycutdiseasedordeadwood,orbranchesthatarerubbingagainsteachotherandthuscausewounds.Thehealthofatreemaybeencouragedbyremovingbranchesthatareblockingupthecentreandsopreventingthefreemovementofair. Oneresultofpruningisthatanopenwoundisleftonthetreeandthisprovidesaneasyentryfordisease,butitisawoundthatwillheal.Oftenthereisaracebetweenthehealingandthediseaseastowhetherthetreewillliveordie,sothatthereisaperiodwhenthetreeisatrisk.Itshouldbetheaimofeverygardenertoreducewhichhasbeenprunedsmoothandclean,forhealingwillbesloweddownbyroughness.Youshouldallowthecutsurfacetodryforafewhurtsandthenpaintitwithoneofthesubstancesavailablefromgardenshopsproducedespeciallyfor thispurpose.Pruningisusuallywithoutinterferencefromtheleavesandalsoitisveryunlikelythatthecutsyoumakewillbleed.Ifthisdoeshappen,itis,ofcourse,impossibletopaintthemproperly. Treesbecomeunhealthyifthegardener__________.
A.allows too many branches to grow in the middle
B.does not protect them from wind
C.forces them to grow too quickly
D.damages some of the small side branches
正确答案是A