题目内容：
根据以下材料，回答题Amongtheraftofbooks,articles,jokes,romanticcomedies,serf-helpguidesandotherwrit-ingsdiscussingmarriage,somefamiliarideasoftencropup.Fewappearmoreoftenthanthe(31)_________thatmanyoldcoupleslookalike.Youhaveprobablyseenitbefore--twoelderlypeoplewalkinghand-in-ha.riddownthestreetorsittingatacafe,(32)_________eachothersostronglythattheycouldbesiblings.Dothesecouplesactuallylookalike,andif(33)_________,whathascausedthemtodevelop
thisway?
AstudypublishedintheMarch2006issueofPersonalityandIndividualDifferencesmayhavethe(34)_________Twenty-twopeople,dividedequally(35)_________maleandfemale,(36)_________inthestudy.Theywereaskedtojudgethelooks,personalitiesandagesof160marriedcouples.Theparticipantsviewedphotographsofmenandwomenseparatelyandwere
(37)_________toldwhowasmarriedto(38)_________Thesubjectsconsistentlyjudgedpeoplewhoweremarried(39)_________beingsimilar(40)_________appearanceandpersonality.
Theresearchersalsofoundthatcoupleswhohadbeentogetherlongerappeared(41)_________similar.
Thisresult(42)_________itselfmaynot-seemsurprising,butthestudyalsoofferedsomean-swerson(43)_________couplesmaylookalike.Tostart,considerthatlifeexperiencescanendup(44)_________reflectedphysically.Someone(45)
ishappyandsmilesmorewilldevel-opthefacialmusclesandwrinklesrelatedtosmiling.Theyearsofexperienceofanelderlycouple'smarriage,happy(46)_________not,wouldthenbereflectedin
their(47)_________
Geneticinfluencesare(48)_________factor.Apaststudyshowedthatgeneticallysimilarpeoplehavebettermarriages.Suchfamilieshave(49)_________incidentsofchildabuseandalow-errateof
miscarriages.Peoplealsoappeartobemoreselfless(50)_________involvedwithgeneti-callysimilarpartners.
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