D
FindWhichDirectionIsSouth
Doyouhaveagoodsenseofdirection?Ifnot,pleasetakewithyouacompass.Butifyouforgettotakeacompass,youcanstillfindyourway.
It’sneveragoodideatoimaginethatthefamilymemberwhowasentr usted（委托）withthejobofmap-readingactuallyknowswherethefamilyis.Youcantellbytheslightlyconfusedloadontheirfacesthatnothingonthegroundseemstomatchthemap.Nevermind.Thesunisshiningandit’sstillmorning.Ifyoudon’tknowtheexacttime,youcanstillfindoutwheresouthis,butyou’llneedtobepatient.
①Findastr aightsickandputitinthegroundinaplacewhereyoucanmarkitsshadow.
②Trytopositionthestickasvertically（垂直）asyoucan.Youcancheckthisbymakingasimpleplumbline（铅锤线）withapieceofstr ingandweight.Youhaven’tgotanystr ing?OK,useathreadfromyourclotheswithabuttontiedattheendtoactasaweight.
③Marktheendoftheshadowcastbythestick.
④Waitapproximatelyhalfanhourandmarktheendoftheshadowagain.
⑤Keepdoingthisuntilyouhavemadeseveralmarks.
⑥Themarknearestthestickwillrepresenttheshortestshadow,whichiscastatmidday,whenthesunishighestintheskyandpointingtotheexactsouth.
⑦Pickapointinthedistancealongthelinebetweentheshortestshadowandthestick.
⑧Thatpointissouthofwhereyouare.
⑨Nowyoucanturnthemap,likeyoudidbefore,andfindwhichwayyoushouldbetr avelling.
68.Tofindthedirection,weoughttobepatientprobablybecause
A.itisnoteasytofindaproperstickB.itisnoteasytopositionthestick
C.ittakeshourstomakethemarksD.ittakesabouthalfanhourtomakethemarks
正确答案：C
