字典翻译 问答 小学 英语 Bananasareoneoftheworld’smostimportantfoodcrops.Theyarealsooneofthemostvaluableexports.Bananasdonotgrowfromseeds.Instead，theygrowfromexistingplants.Bananasarethreatenedbydiseasebecausealltheplantsonafarma
问题标题：
Bananasareoneoftheworld’smostimportantfoodcrops.Theyarealsooneofthemostvaluableexports.Bananasdonotgrowfromseeds.Instead，theygrowfromexistingplants.Bananasarethreatenedbydiseasebecausealltheplantsonafarma
问题描述：

Bananasareoneoftheworld’smostimportantfoodcrops.Theyarealsooneofthemostvaluableexports.Bananasdonotgrowfromseeds.Instead，theygrowfromexistingplants.Bananasarethreatenedbydiseasebecausealltheplantsonafarmarecopiesofeachother.Theyallsharethesamegeneticweaknesses.Forexample，theCavendishbananaismostpopularinNorthAmericanandEuropeanmarkets.However，somekindsoffungusorganismseasilyinfecttheCavendish.BlackSigatokadiseaseaffectstheleavesofCavendishbananaplants.Thediseaseiscontrolledonlargefarmsbyputtingchemicalsontheplant’sleaves.Farmersputanti­fungalchemicalsontheircropsuptoonceaweek.

Anotherfungaldiseaseismoreserious.Panamadiseaseattackstherootsofthebananaplant.Thereisnochemicaltreatmentforthisdisease.Infectedplantsmustbedestroyed.PanamadiseasehasaffectedcropsinSoutheastAsia，AustraliaandSouthAfrica.ThereisconcernthatitmayspreadtobananasgrownintheAmericas.ThiscouldthreatenanimportantexportproductforCentralandSouthAmerica.

TheInternationalNetworkfortheImprovementofBananaandPlantainsupportsresearchonbananas.ThegrouphasheadquartersinFranceandotherofficesinthemajorbanana­growingareasoftheworld.Thegroupsaysthatmoreresearchmustbedonetodevelopimprovedkindsofbananas.Thegroupsaysthatfungaldiseasesmainlyaffectonlyonekindofbanana.Infact，therearefivehundreddifferentkindsofbananas.FoodandAgricultureOrganizationoftheUnitedNationshassaidthattheCavendishbananarepresentsonly10%ofworldproduction.

TheUNagencysaysfarmersshouldgrowdifferentkindsofbananas.Thisprotectsagainstdiseasesthataffectonlyonekind.ExpertswarnthatdiseasemaycausetheCavendishbananatodisappear.Thishappenedearliertoanotherpopularbananabecauseofitsgeneticweaknessagainstdisease.

60．Whatdoesthispassagemainlytellus?

A．Bananasaretheworld’smostimportantfoodcrops.

B．Therisktoapopularbananashowstheneedtogrowotherkinds.

C．Therearefivehundreddifferentkindsofbananas.

D．Howtogrowbananasindifferentcountries.

61．Bananasarethreatenedbydiseasebecause_

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