【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