O字开头的单词或词组
orangeouron purposeonly ifoopsorgyoralorganizedopposeon behalf ofone by oneoutgoingoutstandingomicronoccasionallyodeoutlastovercomeoutweighobligateoverwhelmingonlyoptimisticoracleovalone anotheron no accountoafowe tooccasionon-siteon the spotoptimizeon demandoutoforiginallyoutlineoperativeonce againout of itof oneself