【Coralreefs(珊瑚礁)arenotjustbeautifultolookat，butalsoveryuseful．Theyshelternearly25％ofoceanlifeandprovidefoodforbillionsofpeople．Howeverlikemanyotherspecies，thisamazingecosystem(生态系统)isin】

　　Coralreefs(珊瑚礁)arenotjustbeautifultolookat，butalsoveryuseful．Theyshelternearly25％ofoceanlifeandprovidefoodforbillionsofpeople．Howeverlikemanyotherspecies，thisamazingecosystem(生态系统)isindangerofdyingout!

　　Therearetwomainreasonsforthedestruction—therisingcarbondioxidelevelscausedbyglobalwarmingaswellashumaninfluenceslikebottomoperation．Whilenotmuchcanbedoneabouttheformer，thelosscausedbythelattercanbereduced．

　　Bottomoperationinvolvesdroppingnetstotheoceanbedandthendraggingthemupwhenfilledwithfish．Thisactiondamagedtheoceanfloor，causingthecoralbranchestoseparatefromthereefs．Whilethatisverydiscouraging，thegoodnewsisthatifthesebranchesarefoundquickly，theycanbesaved．Atpresent，thatworkisbeingperformedbyvolunteerdivers.Butthemethodhasonlylimitedsuccessbecausetheycannotstaylongunderwaternorreachdepthsofover200meterswheresomeofthedeep-seacoralgrows．

　　However，thisisnotthecaseforCoralbots—therobotsthatcanconstantlyseekoutbrokenbranches．Ateamof‘coralbots’，eachindividuallyworkingtosimpleruleswillpiecetogether’damagedbitsofcoralallowingthemtoregrow.Theyareprogrammedtobeabletodistinguishbetweenotherthingsandthecoral．Therobotsworktogetheringroups，similartobees．Ifonecoralbotisdamagedthentheotherswillstillbeabletocompletethetask．

　　DrLea-AnneHenrysaid：“Theprojectofusingcoralbotsoffersusthepossibilitytorestore(修复)thefunctionofreefs．Itisinthefinalstageoftesting．OncereadytheresearchershopetobuildhundredsofthemandusethemeffectivelyinthewatersoffScotlandandthenhopefullyintheoceansacrosstheworld．”

　　1.Whichofthefollowingisacauseofthedangerthatcoralreefsarefacing?

　　A．Theappearanceofnewcreatures．

　　B．Theseriouslypollutedseawater．

　　C．Theactivitiesofvolunteerdivers．

　　D．Humanactivitieslikebottomoperation．

　　2.Comparedwithvolunteerdivers，coralbots______________．

　　A．canstaylongerunderwater

　　B．mustworkasbeesdo

　　C．candistinguishwhatiscoral

　　D．canneverbedamaged

　　3.Whatdoestheunderline