PassageTwoQuestions7to11arebasedonthefollowingpassage.Thewaterlevelofoceansrisesandfallsalternately(交替地)twiceaday.Thismovementofwateriscalledthetide(潮汐).Tidesarecausedbythepullofthesunandthemoonontheearth’ssurface;sincethemooniscloser,itaffectsthetidesmorethanthesun.Whenthemoonisdirectlyoverhead,itactuallypullsonthewaterthatisbelowit.Thiscausesthewaterleveltorisebecausethewaterispulledawayfromtheearth.Asthemoondisappearsoverthehorizon(地平线),thepulllessensandthewaterlevelsettlesbacktowardstheoceanbottom.Whenthewaterreachesitshighestlevel,wehavehightide.Andwhenthewatercomestoitslowestlevel,wehavelowtide.Fromitslowestpoint,thewaterrisesgraduallyforaboutsixhoursuntilitreacheshightide.Thenitbeginstofallcontinuouslyforaboutsixhoursuntilitreacheslowtide.Thenthecyclebeginsagain.7.Whichofthefollowingmightbethebesttitleforthepassage?
D
The Pull of the Moon and the Sun
