根据下列内容，回答201-205题。 Inthelate1960s,manypeopleinNorthAmericaturnedtheirattentiontoenvironmentalproblems,andnewsteel-and-glassskyscraperswerewidelycriticized.Ecologistspointedoutthataclusteroftallbuildingsinacityoftentransportationandparkinglotcapacities. Skyscrapersarealsolavishconsumers,andwastersofelectricpower.Inonerecentyear,theadditionof17millionsquarefeetofskyscraperofficespaceinNewYorkCityraisedthepeakdailydemandforelectricityby120,000kilowatts--enoughtosupplytheentirecityofAlbany,NewYork,foraday. Glass-walledskyscraperscanbeespeciallywasteful.Theheatloss(orgain)throughawallofhalf-inchplateglassismorethantentimesthatthroughatypicalmasonrywallfilledwithinsula-tionboard.Tolessenthestrainonheatingandair-conditioningequipment,buildersofskyscrapershavebeguntousedouble-glazedpanelsofglass,andreflectiveglassescoatedwithsilverorgoldmirrorfilmsthatreduceglareaswellasheatgain.However,mirror-walledskyscrapersraisethetemperatureofthesurroundingairandaffectneighboringbuildings. Skyscrapersputaseverestrainonacity'ssanitationfacilities,too.Iffullyoccupied,thetwoWorldTradeCentertowersinNewYorkCitywouldalonegenerate2.25milliongallonsofrawsewageeachyear--asmuchasacitythesizeofStamford,Connecticut,whichhasapopulationofmorethan109,000. Skyscrapersalsointerferewithtelevisionreception,blockbirdflyways,andobstructairtraf-fic.InBostoninthelate1960s,somepeopleevenfearedthatshadowsfromskyscraperswouldkillthegrassonBostonCommon. Still,peoplecontinuetobuildskyscrapersforallthereasonsthattheyhavealwaysbuiltthem--personalambition,civicpride,andthedesireofownerstohavethelargestpossibleamountofrentablespace. Themainpurposeofthepassageisto__________.
A.discuss the advantages and disadvantages of skyscrapers B.compare skyscrapers with other modern structures C.describe skyscrapers and their effect on the environment D.illustrate various architectural正确答案C
