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 failedThe country has already sent up three unmanned spacecrafts,th

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 failedThe country has already sent up three unmanned spacecrafts,th
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,

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 failedThe country has already sent up three unmanned spacecrafts,th
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?否则是什么成分就不知道了,是吧?所以应该把have 变为having ,现在分词作状语用.
2.A Reason:"The country has already sent up three unmanned spacecrafts" 已经是一个完整的句子了,所以C项就排除了；因为前一句已经是用了现在完成时了,而且,从the most rescent中也能看出,应该是已经发生的事,所以不能用不定式,所以B项就排除了；再者事情不是在现在发生的,所以不能用进行时,所以D项也就排除了；答案就只剩下A了.
3.B Reason:" --that she didn't do a good job"中的didn't 是过去式,所以不可能与将来时或者现在进行时公用,所以A,C,D都排除了.
4.A Reason：本句可以改写为---Rooftops that are /were covered with plants are / were called "gernn roofs“,which could help fight global warmiing.其中 that are / were covered 作为同位语状语成分,若是去掉先行词,则只需把that 和be 动词去掉就可以了,没必要把be 动词变成being.因为你可以想啊,屋顶又不是只是现在被覆盖了植被是不?不合情理啊,事实上是这是一种通俗说法,而could 也只表示猜测,并非强调过去时,这也是我为何在改写句中写了 are/ were,这就因个人想法而定了.我本人认为应用are,但可能他人有不同想法.
希望以上对你有所帮助,要是可以的话,毕竟我花了好久分析并打字的.

having done一般都用在句首，动作发生在句中另一个动词之前。第一句中：打电话没找到他们发生在前，发短信发生在后。