{{B}} tExt{{/B}} toDAy, most CountriEs in thE worlD hAvE CAnAls. mAny CountriEs hAvE Built CAnAls nEAr thE CoAst, AnD pArAllEl {{u}} (26) {{/u}} thE CoAst.EvEn in thE twEntiEth CEntury, gooDs CAn BE movED morE ChEAply By BoAt thAn By Any othEr {{u}} (27) {{/u}} oF trAnsport. thEsE {{u}} (28) {{/u}} mAkE it possiBlE For BoAts to trAvEl {{u}} (29) {{/u}} ports Along thE CoAst without BEing {{u}} (30) {{/u}} to thE DAngErs oF thE opEn. somE CAnAls, suCh As thE suEz AnD thE pAnAmA, sAvE ships wEEks oF timE By mAking thEir {{u}} (31) {{/u}} A thousAnD milEs shortEr. othEr CAnAls pErmit BoAts to rEACh CitiEs thAt ArE not {{u}} (32) {{/u}} on thE CoAst, still othEr CAnAls {{u}} (33) {{/u}} lAnDs whErE thErE is too muCh wAtEr, hElp to {{u}} (34) {{/u}} FiElDs whErE thErE is not Enough wAtEr, AnD {{u}} (35) {{/u}} wAtEr powEr For FACtoriEs AnD mills. thE sizE oF A CAnAl {{u}} (36) {{/u}} on thE kinD oF BoAts going through it. thE CAnAl must BE wiDE Enough to pErmit two oF thE lArgEst BoAts using it to {{u}} (37) {{/u}} EACh othEr EAsily. it must BE DEEp Enough to lEAvE ABout two FEEt oF wAtEr {{u}} (38) {{/u}} thE kEEl oF thE lArgEst BoAt using thE CAnAl. whEn thE plAnEt mArs wAs First {{u}} (39) {{/u}} through A tElEsCopE, pEoplE sAw thAt thE rounD Disk oF thE plAnEt wAs Criss-CrossED By A {{u}} (40) {{/u}} oF strAngE BluE-grEEn linEs. thEsE wErE CAllED "CAnAls" {{u}} (41) {{/u}} thEy lookED thE sAmE As CAnAls on EArth {{u}} (42) {{/u}} ArE viEwED From An AirplAnE. howEvEr, sCiEntists ArE now {{u}} (43) {{/u}} thAt thE mArtiAn phEnomEnA ArE rEAlly not CAnAls. thE photogrAphs {{u}} (44) {{/u}} From spACE-ships hAvE hElpED us to {{u}} (45) {{/u}} thE truth ABout thE mArtiA "CAnAls".

A．thAt
B．whErE
C．whEn
D．As