非謂語動詞里的having done什么時候用呢?
我知道二者有時間區(qū)別,可到底怎么區(qū)分呢?
－－to reach them on the phone,we sent an email instead.
A.Failed B.Having failed
The country has already sent up three unmanned spacecrafts,the most recent（）at the end of last month.
A.having been launched D.to be launched C.has been launched D.being launched
--that she didn't do a good job,i don't think i am abler than her.
A.To have said B.Having said C.To say D.Saying
Rooftops()with plants,called"gernn roofs",could help fight global warming.
A.covered B.being covered
求詳解,