beaches, birds, boxes, cats, classrooms,
classmates,dolphins,dumplings, elephants,
giraffes,groups,gyms,hospitals,houses,keys,key rings,koalas,leaf,leaves,library
lions,magazines,mails,malls,maps,mountains,mewspapers,noodles,onions,pandas, pen pals ,penguins,potatoes,reasons,rules
,scarf-scarf或scarves,thief-thieves,
tigers,toys,units,wallets,zoos,animals,
jobs,doctors,questions,actors,movies,photos.
参考资料：课本上都有啊