题目内容：
根据以下材料，回答题"SeasameStreet"hasbeencalled"thelongeststreetintheworld".
Thisisbecausethetelevisionprogrambythatnamecannowbeseeninsomanypartsoftheworld.
Theprogram,whichwentontheairinNewYorkin1969,usessongs,jokes,andpicturestogivechildrenabasicunderstandingofnumbers,lettersandhumanrelationships.Morethan6million
chil-drenintheUnitedStateswatchitregularly.Theviewers(观众)includemorethanhalfthenation'schildrenbeforeschoolage.
Manyteachersconsidertheprogramagreathelp,thoughsometeachersfindthatproblemshappenwhenthefirst-yearpupilswhohavelearnedfrom"SeasameStreet"areinthesameclassmwiththosewhohavenotwatchedtheprogram.Testshaveshownthatchildrenwhowatchitfivetimesaweeklearnmore
thanthosewhoseldomwatchit.IntheUnitedStatestheprogramisshownatdifferenthoursduringtheweekinordertoincreasethenumberofchildrenwhocanwatchitregularly.
Whyhas'SeasameStreet"beensomuchmoresuccessfulthanotherchildren'sshows?Manyreasonshavebeensuggested.Perhapsonereasonisthatmotherswatch"SeasameStreet"alongwith
theirchildren.Butthebestreasonforthesuccessoftheprogrammaybethatitmakeseverychildwatchingitfeelabletolearn.Thechildfindshimselflearning,andhewantstolearnmore.
Peoplecall"SeasameStreet"thelongeststreetintheworldbecause A．itisthelongestTVprogrameverproduced
B．ittookmuchmoretimetoputonthisprogramthananyotherone
C．itisshownalmostthroughouttheworld
D．ithasbeenontheairsince1969
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