TheGrandCanyon(峡谷)inArizonaextendsfourhundredfiftykilometers.Thecanyonslookasiftheyformedastheearthsplitapart.Theywereactuallycutbyrivers.
LookingattheGrandCanyonislikelookingbackintime.FortymillionyearsagotheColoradoRiverbegancuttingthroughthearea.AtthesametimethesurroundinglandwaspushedupbyforcesdeepwithintheEarth.Rainsnowicewindandplantrootsrubbedawayatthetopofthenewcanyon.Belowtheflowingrivercontinuedtouncovermoreandmorelevelsofancientrock.Theirappearancechangesendlessly--withthelightthetimeofyearandtheweather.
TheGrandCanyonhasseveralweatherenvironments.Thetopisoftenmuchdifferentfromthebottom.Onsomewinterdaysforexampleyoumayfindcoldwindsandsnowatthetop.Butatthebottomyoumayfindwarmwindsandflowers.
TheGrandCanyonisknownasoneofthesevenwondersofthenaturalworld.Aboutfivemillionpeoplevisitthecanyoneachyear.Mostvisitorswalkalongpathspartwaydownintothecanyon.Somevisitorsridemulestothebottomandback.
ThereareseveralotherwaystovisittheGrandCanyon.Hundredsofthousandsofpeopleseethecanyonbyaireachyear.Theypayahelicopterorairplanepilottoflythemaboveandaroundthecanyon.
AbouttwentythousandpeopleayearseetheGrandCanyonfromtheColoradoRiveritself.Theyrideboatsovertherapidrockywater.Thesetripslastfromoneweektothreeweeks.
VisitorscanseetheGrandCanyoninstillanotherway.AhugeglasswalkwaycalledtheSkywalkextendsfromtheedgeandishangingabovethebottomofthecanyon.
SomepeoplesaytheSkywalkisanengineeringwonder.HoweverotherpeoplehavecriticizedtheSkywalkandfuturedevelopment.TheysayitharmsanationaltreasureandreducestheenjoymentofnatureintheGrandCanyon.
1.Wecanlearnfromthefirstparagraph____________.
A.theGrandCanyonisthemostbeautifulplaceinAmerica
B.theGrandCanyonisfourhundredfiftykilometerslong
C.theGrandCanyonusedtobeadriedriver
D.theGrandCanyonusedtobeadeepopeningintheearth
2.AccordingtothepassagepeoplecanvisittheGrandCanyonin______ways.
A.3