这句话错在哪儿了?we have done everything which can be done

这句话错在哪儿了?we have done everything which can be done can't be done.should be done.should have done Everything 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 can be done was done could be done must have been done will 英语学霸进来we have done everything we can yo simply the procedure have done/to be done everything can be done well.换一个说法? If you try your best,everything can be done well they have done everything they can ___the man's life everything i have done is has everything that can be done been done句子里的that能不能省略,为什么?如