These are our sheep. （改为单数句子）

These are our sheep. （改为单数句子） these are our apples改为单数句子 Are these sheep怎么改为单数形式 These are our apples改为单数 These firemen are very helpful.(改为单数句子） These are old chairs(改为单数句子） These men are policemen.【改为单数句子】 These are my photos.改为单数句子 单数句是啥?These are our broths(改为单数句） _____ ______ my brother.应填 These are our books.(改成单数） These are boxes. (改为单数句） These are oranges.(改为单数句）