同步阅读(Unit9)(英文)

(整期优先)网络出版时间:2005-12-22
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你知道什么叫“温室效应”吗?它对地球又有什么样的影响呢?Agreenhouseisabuildingmadeofglasswhichisusedforkeepingoolplantswarmwhentheoutsidetemperatureislow.Inasimilarwaythereareseveralgasesintheatmospherewhichtraptheheatproducedbythesunandpreventitfromescaping.Thesegasesareknownas“greenhousegases”,andthewayinwhichtheytrapheatintheatmosphereiscalled“thegreenhouseeffect”.Thisisnotsimpleairpollution.Mostofthemaingreenhousegasesexistnaturallyinsmallamountsino...