O字开头的单词或词组
once in a whileoppositionodoronboardor elseold-fashionedoakon showorganismorganosoptimismordersongoingon handoasisorbitovercastover timeoctaveout of dateoathon the walloptionalorientationon boardokayobstinateobtainingoverlapobesityoverlookopticalone-pieceonloadold and youngouterovertakeoutletOscarobservationoversee
