精读原文：
AntarcticaandEnvironment
Antarcticahasactuallybecomeakindofspacestationauniqueobservationpostfordetectingimportantchangesintheworld'senvironment. Remotefrommajorsourcesofpollutionandthecomplexgeologicalandecologicalsystemsthatprevailelsewhere, Antarcticamakespossiblescientificmeasurementsthatareoftensharperandeasiertointerpretthanthosemadeinotherpartsoftheworld.
GrowingnumbersofscientiststhereforeseeAntarcticaasadistant-early-warningsensor, wherepotentiallydangerousglobaltrendsmaybespottedbeforetheyshowuptothenorth. Onepromisingfieldofinvestigationisglaciology. ScholarsfromtheUnitedStates, Switzerland, andFrancearepursuingsevenseparatebutrelatedprojectsthatreflecttheirconcernforthehealthoftheWestAntarcticIceSheet一aconcerntheybelievetheworldatlargeshouldshare.
TheTransantarcticMountain, someofthemmorethan 14,000 feethigh, dividethecontinentintotwoverydifferentregions. Thepartofthecontinenttothe "east" ofthemountainsisahighplateaucoveredbyanicesheetnearlytwomilesthick. "West" ofthemountain, thehalfofthecontinentsouthoftheAmericasisalsocoveredbyanicesheet, buttheretheicerestsonrockthatismostlywellbelowsealevel. IftheWestAntarcticIceSheetdisappeared, thewesternpartofthecontinentwouldbereducedtoasparseclusterofisland.
Whileiceandsnowareobviouslycentraltomanyenvironmentalexperiments, othersfocusonthemysterious "dryvalley" ofAntarctica, valleysthatcontainlittleiceorsnoweveninthedepthsofwinter. SlashedthroughthemountainsofsouthernVictoriaLand, thesevalleysonceheldenormousglaciersthatdescended 9,000 feetfromthepolarplateautotheRossSea.
Nowtheglaciersaregone,perhapsacasualtyoftheglobalwarmingtrendduringthe 10,000 yearssincetheiceage. Eventhesnowthatfallsinthedryvalleysisblastedoutbyviciouswindsthatroarsdownfromthepolarplateautothesea. Leftbarearespectaculargorges, rippledfieldsofsanddunes, clustersofboulderssculpturedintofantasticshapesby 100-mile-an-hourwinds, andanauraofextraterrestrialdesolation.
Despitetheunearthlyaspectofthedryvalleys, somescientistsbelievetheymaycarryamessageofhopeoftheverdantpartsoftheearth. Somescientistsbelievethatinsomecasesthedryvalleysmaysoakuppollutantsfasterthanpollutantsenterthem.
【阅读练习题】
1.Whatisthebesttitleforthispassage?
[A] AntarcticaandenvironmentalProblems.
[B]Antarctica: Earth'sEarly-Warningstation.
[C] Antarctica: aUniqueObservationPost.
[D] Antarctica: aMysteriousPlace.
2.WhatwouldtheresultbeiftheWestAntarcticIceSheetdisappeared?
[A] Thewesternpartofthecontinentwouldbedisappeared.
[B]Thewesternpartofthecontinentwouldbereduced.
[C] ThewesternpartofthecontinentwouldbecomescatteredIslands.
[D] ThewesternpartofthecontinentwouldbereducedtoaclusterofIslands.
3.WhyaretheDryValleysleftbare?
[A] Viciouswindblaststhesnowaway.
[B]Itrarelysnows.
[C] Becauseof