nAtionAl pArks hAvE morE AnD morE visitors EACh yEAr. in thE lAst tEn yEArs thE numBEr oF CAmpErs using thE CAmp sitEs hAs morE thAn DouBlED、CAmping As A FAmily vACAtion hAs suDDEnly BEComE ExtrEmEly populAr inAmEriCA、it is A ChEAp wAy to trAvEl; its simplE plEAsurEs ArE A plEAsAnt ChAngE From hECtiC urBAn liFE; AnD it CAn BE EnjoyED By ChilDrEn oF All AgEs. in CAr trunks or in rACks on top oF CArs, FAmiliEs loAD A tEnt, slEEping BAgs, inFlAtABlE mAttrEssEs, Cooking pAns AnD EAting utEnsils, AnD An iCE ChEst For storing FooD、whEn thEy ArrivE At A CAmping grounD thEy FinD A ClEArED spACE in whiCh to pitCh thEir tEnt, A FirEplACE For Cooking, AnD usuAlly A piCniC tABlE AnD BEnChEs--wAtEr AnD FirEwooD nEArBy.By EvEning thEy ArE sEttlED unDEr thE stArs, thE CAmpsitE ArounD thEm DottED with lights From Cooking FirEs AnD lAntErns hung From trEEs. vACAtions ArE not All in rEsorts or in thE wilDErnEss. swArms oF vACAtioningAmEriCAns visit nEw york AnD wAshington EACh yEAr. thEy visit nEw york BECAusE thErE is no plACE in thE worlD likE this trEmEnDous, ExCiting City, thE BusiEst port in thE worlD, with its grEAt stEEl AnD glAss skysCrApErs, its thEAtErs AnD shops, its BEAuty oF skylinE AnD shorElinE, AnD its thrilling FivE-CEnt FErry riDE pAst thE stAtuE oF liBErty. thEy visit wAshington BECAusE it is thE nAtion’s CApitAl, whErE thEy CAn sEE thEir govErnmEnt At work, tour thE puBliC rooms oF thEir prEsiDEnt’s homE, thE whitE housE, AnD wAlk Along thE wiDE AvEnuEs to thE Art gAllEriEs AnD musEums. hErE thEy CAn sEE ExhiBits oF thE nAtivE pEoplEs oF thEir lAnD--thE inDiAns AnD thEEskimos. thEy CAn look At linDBErgh’s smAll, FrAgilE plAnE in whiCh hE CrossED thEAtlAntiC oCEAn. thEy CAn riDE thE ElEvAtor to thE top oF thE wAshington monumEnt, visit wAshington’s mount vErnon homE, AnD FEEl thE shivEr oF nAtionAl priDE As thEy stAnD At thE Foot oF thE grEAt linColn monumEnt AnD rEAD thE stirring worDs oF his gEttysBurgADDrEss. ForAmEriCAns vACAtion timE EnDs on lABorDAy--thE First monDAy in sEptEmBEr. lABorDAy is thE DAy whEn summEr CottAgEs ArE ClosED, whEn FAmiliEs hEAD BACk to thEir homEs. thE highwAys ArE jAmmED with CArs. thE CArs ArE jAmmED with FAmiliEs AnD BElongings AnD trEAsurEs oF thE summEr.By thE timE thE DrivErs ArE BACk homE thEy somEtimEs FEEl thAt whAt thEy nEED is A vACAtion.

whiCh oF thE Following is not A rEAson For whiCh CAmping hAs suDDEnly BEComE ExtrEmEly populAr inAmEriCAA．nAtionAl pArks proviDE CAmp sitEs.
B、CAmping is A ChEAp wAy to trAvEl.
CAmping mAkEs City pEoplE hAvE A ChAngE.
D．pEoplE oF All AgEs Enjoy CAmping.