托福阅读阅读细节题专题.doc

1,Inviewofthesefacts,scientistshypothesizedthatasinglelargeasteroid,about10to15kilometersacross,collidedwithEarth,andtheresultingfalloutcreatedtheboundaryclay.Theircalculationsshowthattheimpactkickedupadustcloudthatcutoffsunlightforseveralmonths,inhibitingphotosynthesisinplants;decreasedsurfacetemperaturesoncontinentstobelowfreezing;causedextremeepisodesofacidrain;andsignificantlyraisedlong-termglobaltemperaturesthroughthegreenhouseeffect.Thisdisruptionoffoodchainandclimatewouldhaveeradicatedthedinosaursandotherorganismsinlessthanfiftyyears.考虑到这些事实，科学家们就假设有一个较大的小行星，直径差不多有10到15公里，曾与地球相撞，所以碰撞扬起的灰尘等就形成了这层粘土层。他们的计算表明撞击扬起的灰尘遮挡了阳光达几个月之久，阻止了植物的光合作用，将陆地上的气温降到了零点之下，导致酸雨，通过温室效应造成了长期的、严重的全球升温。这种对食物链和气候的极大扰乱将可使恐龙和其他生物在不到50年的时间内绝迹。
T8(2)12#

12.Paragraph6mentionsallofthefollowingeffectsofthehypothesizedasteroidcollisionEXCEPT12.EXCEPT题，排除法。A的dustcloud，B的dropinthesurfacetemperatures和D的increaseinglobaltemperatures都能定位至第二句，都正确，不选；C的rainfall原文没说，错，选

○alargedustcloudthatblockedsunlight
○animmediatedropinthesurfacetemperaturesofthecontinents
○anextremedecreaseinrainfallonthecontinents
○along-termincreaseinglobaltemperatures

2,SomescientistsspeculatethatMarsmayhaveenjoyedanextendedearlyPeriodduringwhichrivers,lakes,andperhapsevenoceansadorneditssurface.A2003MarsGlobalSurveyorimageshowswhatmissionspecialiststhinkmaybeadelta―afan-shapednetworkofchannelsandsedimentswhereariveronceflowedintoalargerbodyofwater,inthiscasealakefillingacraterinthesouthernhighlands.Otherresearchersgoevenfurther,suggestingthatthedataprovideevidenceforlargeopenexpensesofwaterontheearlyMartiansurface.Acomputer-generatedviewoftheMartiannorthpolarregionshowstheextentofwhatmayhavebeenanancientoceancoveringmuchofthenorthernlowlands.TheHellasBasin,whichmeasuressome3,000kilometersacrossandhasafloorthatliesnearly9kilometersbelowthebasin’srim,isanothercandidateforanancientMartiansea.一些科学家认为早期的火星上广泛存在着河流，湖泊甚至是海洋。一份2003年的对火星全球的调查照片显示了一个科学家们认为是三角洲的构造——一个扇形的沉积物和水流通道的网络，河流可能是从这里流入了一个更大的水体；在这种情况下，它可能是南部高地的一个火山口湖泊。其他研究者做了更大胆的