请问They are American apples.的单数形式

请问They are American apples.的单数形式 are they apples?改为单数形式 are they american students?改为单数形式 they are apples改为单数 把They are apples.改为单数句 they are some apples 改单数：---------- ------------- ---------- What are these?They are apples的单三形式 are these apples?改为单数形式 these are apples 改为单数形式 where are their apples 单数形式 These are apples变成单数形式 These are apples改为单数形式