Whatever has been done in the world's history can be done ag

all that can be done has been done Everything that can be done has been done,___? Has all that can be done been done? all that can be done has been done. Everything can be done has been done.请问这里can be done 用的是什么时态 all that can be done been done. all that can be done has been done 为什么要用has,不用have America has never been about what can be done for what has been done can not be undone I don't think anything that has been done can be done.怎么翻译 all that can be done has been done.中的that为 has everything that can be done been done句子里的that能不能省略,为什么?如