I did all I could(do) to help the poorwhy the "do"behind "could"can be left out?

I did all I could(do) to help the poorwhy the dobehind couldcan be left out? If I could do it all again All I did was to do my homework.all I did是什么用法啊? All i could do is to wait.的主语是I could do''吗 i wish i could see you againa so could ib so do i c so did id so had i I did ---to help the poor.A.all what l could B.all which l could C.all l could D.all the thingswhat l could I could face it all 翻译All I could do was that I lent you a dictionary. I learned to laugh when all I could do was cry.”是什么意思? 英语翻译I was flexin’,anticipating.I was wondering what I could say I was driving around,around in circles,It’s a miracle I stayed away.All I want to do is hold you tight,Would you object if I called you mine?Did you hear me right?I’ll do y i did not tell you XIAOWANG could do the job.句子陈分咋画 i did not tell you XIAO WANG could do the job.咋改被动语态 I wonder if you could do me a favor?A、Sure B、I could C、Yes,I do D、No,not at all 选什么回答 how did i do意思 what did i do to How did i do well? Tom and Jack?I did't believe they could do the work.是选C么?A.So did I.B.So I did't .C .Neither did I D.Me too. I would appreciate it (if you do sth./ if you did sth./ if you could do sth.)都可以吗?I would appreciate it (if you do sth./if you did sth./ if you could do sth.)都可以吗?