This song is often sung by children.（含被动语态）
This house was built in 1958.
Many buildings will be built in my home town.
He asked me how soon I would get ready.
The proposal is being considered now.
I will be reading a book at 10:00 tomorrow.
He asked me what I should be doing six o'clock tomorrow.
Have the letters been posted ?
He came and told us that the work had been finished.
I thought Sophia would have told you something.
完成进行时/have been doing（强调持续性）
We have been seeing quite a lot of each other recently.
He has been saying that for years.
He will have been studying Chinese seven years by 1980．
I knew by that time he would have been working there for 30 years.
We hope that there will be many people at your party today.
He said he was writing a novel.
Our suggestion is that you（should）be the first to go．