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