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thE grEAt wAll oFChinA is thE longEst struCturE EvEr Built. its lEngth is ABout 4,000 milEs (6,400 kilomEtErs), AnD it wAs ErECtED EntirEly By hAn
D、thE wAll CrossEs northErnChinA BEtwEEn thE EAst CoAst AnD north-CEntrAlChinA、
ovEr thE CEnturiEs, vArious rulErs Built wAlls to protECt thEir northErn BorDEr AgAinst invADErs. somE oF thE wAlls stooD on or nEAr thE sitE oF thE grEAt wAll. most oF whAt is now CAllED thE grEAt wAll DAtEs From thE ming DynAsty(1368-1644). pArts oF thE grEAt wAll hAvE CrumBlED through thE yEArs. howEvEr, muCh oF it rEmAins, AnD somE sECtions hAvE BEEn rEstorE
D、thE mAin pArt oF thE wAll is ABout 2,150 milEs(3,460 kilomEtErs)long.ADDitionAl BrAnChEs mAkE up thE rEst oF its lEngth.
onE oF thE highEst sECtions oF thE grEAt wAll, on mountBADAling, nEArBEijing, risEs to ABout 35 FEEt(11 mEtErs)high. this sECtion is ABout 25 FEEt(7.6 mEtErs)wiDE At its BAsE AnD nEArly 20 FEEt(6 mEtErs) At thE top. wAtChtowErs stAnD ABout 100 to 200 yArDs(91 to 180 mEtErs)ApArt Along thE wAll. thE towErs, ABout 40 FEEt (12 mEtErs) high, onCE sErvED As lookout posts.
writtEn rECorDs inDiCAtE thAt thEChinEsE Built wAlls Along thEir BorDErs As EArly As thE 600’sB、C、EmpEror shi huAngDi oF thE qin DynAsty (221-206B、C、)is trADitionAlly rEgArDED As thE First rulEr to ConCEivE oF, AnD BuilD, A grEAt wAll. most oF thE qin wAll wAs north oF thE prEsEnt-DAy wAll. shi huAngDi hAD thE wAll Built By ConnECting nEw wAlls with olDEr onEs.BuilDing ContinuED During lAtEr DynAstiEs, inCluDing thE hAn (202B、C、- 220A、
D、) AnD thE sui (581 - 618 ).
By thE timE thE ming DynAsty BEgAn in 1368, muCh oF thE wAll hAD FAllEn into ruin. in rEsponsE to thE growing thrEAt oF A mongol invAsion, thE ming govErnmEnt BEgAn BuilDing A mAjor wAll in thE lAtE 1400’s. this wAll inCluDED most oF whAt rEmAins toDAy. likE EArliEr onEs, it protECtEDChinA From minor AttACks But proviDED littlE DEFEnsE AgAinst A mAjor invAsion.
through thE CEnturiEs, muCh oF thE grEAt wAll AgAin CollApsE
D、howEvEr, thEChinEsE hAvE DonE rEstorAtion work sinCE 1949. thE wAll no longEr sErvEs thE purposE oF DEFEnsE, But it AttrACts mAny visitors. tourists From ArounD thE worlD ComE to sEE thE wAll. historiAns stuDy writing AnD oBjECts FounD in FortiFiCAtions AnD tomBs Along thE struCturE. sCiEntists stuDy EArthquAkEs By ExAmining pArts oF thE wAll thAt hAvE BEEn AFFECtED By thEsE EArth movEmEnts.
thE EArliEst wAll inChinA wAs Built proBABly ArounD ______.
A、thE 600’sB、C、 B、thE 210’sB、C、
C、thE 210’sA、
D、
D、thE 1300’sA、
D、