Riversareoneofourmostimportantnaturalresources(资源).Manyoftheworld’sgreatcitiesarelocatedonriversandalmosteverycountryhasatleastoneriverrunningthroughitthatplaysanimportantpartinthelivesofitspeople.

　Sincethebeginningofhistorypeoplehaveusedriversfortransportation.ThelongestoneintheUnitedStatesistheMississippi.ThelifelineofEgyptistheNile.TothepeopleofIndiatheGangesisgreatbutitisalsoimportantfortransportation;shipscantravelalongitforathousandmiles.OthergreatriversaretheCongoinAfricaandtheMekonginsoutheasternAsia.Thegreatestofallfornavigation（航海）howeveristheAmazoninBrazil（巴西）.Itissowideandsodeepthatlargeshipscangoabouttwothousandmilesupit.

Besidestransportationriversgivefoodtoeatwatertodrinkwaterforcropsandchancesforfun.Inordertoincreasethesupply(供给)ofwaterforcropsengineerssometimesbuildadam(大坝)acrossariverandletalakeformbehindthedam.Thenpeoplecanusethewaternotonlytoirrigate(灌溉)theirfieldsbutalsotomakeelectricityfortheirhomesandindustries.

　Howeverlargecitiesandindustriesthatarelocatedonriversoftencauseproblems.Asthecitiesgrowinsizeandindustriesincreaseinnumberthewaterintheriversbecomespollutedwithchemicalsandothermaterials.Peoplearelearningtheimportancehoweverofdoingmoretokeeptheirriverscleaniftheywanttoenjoythebenefitsofthesenaturalresources.

1．Thegreatestriverfornavigationis________________.

　A.theMississippi　B.theNile　

C.theMekongD.theAmazon

2．WhichisNOTtrueaccordingtothepassage?

A.Manycitiesarelocatedonrivers.

B.Almosteverycountryhasatleastoneimportantriver.

C.TheNileisinIndia.

D.Riversplayanimportantpartinthelivesofpeople.

3．Whenriversaredammedpeopleusethewaterfor__________.

A.keepingtheriversclean

B.makingelectricity

C.washingclothes

D.irrigationandtheproductionofelectricity

4．Mostwaterinriversispollutedwith___________.

A.people’sdrinkingwatertoomuch

B.people’sswimmingintherivertoomuch