Поставьте сущ. в единственное число. Aircraft,brothers-in-arms,brothers-in-law,cuckoos,deer,feet,flies,girl-friends,hairdos,keys,languages,leaves,lice,mice,Negroes ,parties,pianos,foofs,sheep,skies,taxes,taxis,theses,tomatoes,zeros.
Aircraft brother-in arm (?) - - deer foot fly girlfriend - key language leaf louse mouse - part piano - sheep sky tax taxi - tomato zero