单选题 Picturethis:You’reatamovietheaterfoodstandloadinguponsnacks.Youhaveachoiceofasmall,mediumorlargesoda.Thesmallis$3.50andthelargeis$5.50.It’satoughdecision:Thesmallsizemaynotlastyouthroughthewholemovie,but$5.50forsomesugarydrinkseemsridiculous.Butthere’sathirdoption,amediumsodafor$5.25.Mediummaybetheperfectamountofsodaforyou,butthelargeisonlyaquartermore.Ifyou’relikemostpeople,youendupbuyingthelarge(andtakingabathroombreakmidshow).Ifyou’rewonderingwhowouldbuythemediumsoda,theanswerisalmostnoone.Infact,there’sagoodchancethemarketingdepartmentpurposelypricedthemediumsodaasadecoy(诱饵),makingyoumorelikelytobuythelargesodaratherthanthesmall.IhavewrittenaboutthispeculiarityinhumannaturebeforewithmyfriendDanAriely,whostudiedthisphenomenonextensivelyafternoticingpricingforsubscriptions(订阅)toTheEconomist.Thedigitalsubscriptionwas$59,theprintsubscriptionwas$125,andtheprintplusdigitalsubscriptionwasalso$125.Nooneintheirrightmindwouldbuytheprintsubscriptionwhenyoucouldgetdigitalaswellforthesameprice,sowhywasitevenanoption?Arielyrananexperimentandfoundthatwhenonlythetwo"real"choiceswereoffered,morepeoplechosetheless-expensivedigitalsubscription.Buttheadditionofthebadoptionmadepeoplemuchmorelikelytochoosethemoreexpensiveprintplusdigitaloption.Brainscientistscallthiseffect"asymmetricdominance"anditmeansthatpeoplegravitatetowardthechoicenearestaclearlyinferioroption.Marketingprofessorscallitthedecoyeffect,whichiscertainlyeasiertoremember.Luckyforconsumers,almostnooneinthebusinesscommunityunderstandsit.Thedecoyeffectworksbecauseofthewayourbrainsassignvaluewhenmakingchoices.Valueisalmostneverabsolute;rather,wedecideanobject’svaluerelativetoourotherchoices.Ifmoreoptionsareintroduced,thevalueequationchanges.问：Howdoweassessthevalueofacommodity,accordingtothepassage?