Australia’sfrogsarehavingtroublefindinglove.Trafficnoiseandothersoundsofcitylife,suchasairconditionersandconstructionnoise,aredrowningoutthematingcallsofmalefrogsinurbanareas,1eadingtoasharpdropinfrogpopulations.But,inthefirststudyofitskind,Parris,ascientistattheUniversityofMelbournehasfoundthatsomefrogshavefiguredoutawaytocompensateforhumaninterferenceintheirlovelives. Amalesouthernbrowntreefrogsendsoutamatingcallwhenhe’slookingforadate.Itismusictotheearsofafemalesouthernbrowntreefrog.But,addthesoundsofnearbytrafficandthemessagejustisnotgoingout.ParrisspentsevenyearsstudyingfrogsaroundMelbourne.Shesayssomefrogshavecomeupwithaninterestingstrategyformakingthemselvesheard. “Wefoundthatit’schangingthepitchofitscall,sogoinghigherup,upthefrequencyspectrum,beinghigherandsqueakier,furtherawayfromthetrafficnoiseandthisincreasesthedistanceoverwhichitcanbeforheard,”Parrissaid. Theoldcallislowerinpitch.Thenewoneishigherinpitch. Now,thatmaysoundlikeaprettysimplesolution.But,changingtheircallstocopewithanoisyenvironmentisactuallyquiteextraordinaryforfrogs.Andwhilethemaleshavefiguredouthowtomakethemselvesheardabovethenoise,Parrissaysitmaynotbewhatthefemalesarelookingfor. “Whenfemaleshaveachoicebetweentwomalescalling,theytendtoselecttheonethatcallsatalowerfrequencybecause,infrogs,thefrequencyofacallisrelatedtobodysize.So,thebiggerfrogstendtocalllower,”sheexplained.“Andsotheyalsotendtobetheolderfrogs,theguysperhapswithmoreexperience,theyknowwhatthey’redoingandthewomenareattractedtothose.” FrogpopulationsinMelbournehavedroppedconsiderablysinceParrisbeganherresearch,butitisnotjustbecauseofnoise.MuchofAustraliahasbeenlockedina10-yeardrought,leavingfrogsfewerandfewerpondstogolookingforthatspecialsomeone. Whatdoestheword“considerably”inthelastparagraphmean?
A.immediately
B.directly
C.carefully
D.much
正确答案是D