题目

非谓语动词里的having done什么时候用呢?
我知道二者有时间区别,可到底怎么区分呢?
－－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
求详解,

提问时间：2020-10-23

答案

1.B Reason:Having failed 是作为原因状语成分的,可以改写为——Because we have failed to reach them on the phone,we sent an e-mail instead.把 Because we 去掉,但是总不可能让动词直接放句首吧?否则是什么成分...