All __ done now.为什么要填has 而不填have been和have?

All __ done now.为什么要填has 而不填have been和have? all that can be done has been done 为什么要用has,不用have if you had followed the doctor's advice,you ___ all right now.A would be B would be done为什么A另外虚拟语气怎么用的 All can be done. All must be done.合并为一个句子怎么写? 为什么? 英语语法习题能否解释以下习题:1．Neither Tom nor his parents ___ at home.A.is B.are C.has been D.was这题为何要选B2.All that can be done ____.A.has been done B.has done.C.have done D.were done这题为何要选A3.There __ in this r ——How dare you talk to your teacher like that?——Well,now i regret ever （having done） that.为什么要用having done now i regret having done改成to have done不行吗?为什么? all that can be done has been done.中的that为all that can be done has been done.中的that为什么不能用which替换? all that can be done has been done为什么用HAS The government has done a lot of work for blind people.Now they can walk __(safe) than before. I will tell her __ he told me yesterday.为什么不用all which which that?而要用all which? __ the children __ （fly）kites __ （happy）in the garden now?Yes.They all feel __ （happy）. all后面用is还是areAll .here now,Let's startyou are late All.done now...中间填is 或are 37.____can be done _____been done.A.All； have B.All that； haveC.All；has D.All that；has我选了A 为什么错了. All that can be done___A.have been done B.have done C.has been done D.has done为什么选C怎么解释? if you had followed the doctor's advice, you ___ all right now.A would be B would be doneC would have been为什么A虚拟语气主句不是would have done么阿! 动词的正确形式All but one __ (be)here just now. Thank you for all you have done for you为什么all后不加that