PassageTwo
Questions26to30arebasedonthefollowingpassage.
Tidesarecreatedmainlybythepullofthemoonontheearth.Themoon'spullcauseswaterintheoceanstobealittledeeperatapointclosesttothemoonandalsoatapointfarthestfromthemoon,ontheoppositesideoftheearth.Thesetwotidal“waves”followtheapparentmovementofthemoonaroundtheearthandstr ikenearlyeverycoastlineatintervalsofabouttwelvehoursandtwenty-fiveminutes.Afterreachingahighpoint,thewaterlevelgoesdowngraduallyforalittlemorethansixhoursandthenbeginstorisetowardanewhighpoint.Hence,mostcoastlineshavetwotidesaday,andthetidesoccurfiftyminuteslatereachday.Differencesinthecoastlineandinchannelsintheoceanbottommaychangethetimethatthetidalwavereachesdifferentpointsalongthesamecoastline.Thedifferenceinwaterlevelbetweenhighandlowtidevariesfromdaytodayaccordingtotherelativepositionsofthesunandthemoon.Thesunalsoexertsapullontheearth,althoughitisonlyabouthaftasstr ongasthepullofthetidesarisehigherandwhentheypullatr ightanglestooneanother.thetideislower.Theformationofthecoastlineandvariationsintheweatherareadditionalfactorswhichcanaffecttheheightoftides.Somesectionsofthecoastareshapedinsuchawayastocausemuchhighertidesthanareexperiencedinotherareas.Astr ongwindblowingtowardtheshoremayalsocausetidestothehigher.
Whichofthefollowingisrightaccordingtothepassage?
A.Somecoastlinesdonothavetwotideseachday.
B.Tidesarenotaffectedbytheshapeofcoastline.
C.Thesunhasasmucheffectontidesasdoesthemoon.
D.Tidesusuallyrisetothesamelanddayafterday.
正确答案：A[解析]从文中可知B，C，D不涉及潮汐运动，故选A。
