1) 表示目的;它的否定式是so as not to do。
Tom kept quiet about the accident so as not to lose his job.
Go in quietly so as not to wake the baby.
2) so kind as to ---劳驾
Would you be so kind as to tell me the time?
注意： 当有though, although时，后面的从句不能有but，但是 though 和yet可连用
Although it‘s raining, they are still working in the field.
He is very old, but he still works very hard.
Though the sore be healed, yet a scar may remain.
1) ___she is young, she knows quite a lot.
A. When B. However C. Although D. Unless
2) as, though 引导的倒装句
as / though引导的让步从句必须表语或状语提前(形容词、副词、分词、实义动词提前)。
Child as /though he was, he knew what was the right thing to do.
= Though he was a small child, he knew what was the right thing to do.
注意： a. 句首名词不能带任何冠词。
Try hard as he will, he never seems able to do the work satisfactorily.
= Though he tries hard, he never seems…
3) ever if, even though. 即使
We‘ll make a trip even though the weather is bad.
4) whether…or- 不管……都
Whether you believe it or not, it is true.
5) "no matter +疑问词" 或"疑问词+后缀ever"
No matter what happened, he would not mind.
Whatever happened, he would not mind.
替换：no matter what = whatever
no matter who = whoever
no matter when = whenever
no matter where = wherever
no matter which = whichever
no matter how = however
注意：no matter 不能引导主语从句和宾语从句。
(错)No matter what you say is of no use now.
(对)Whatever you say is of no use now.
你现在说什么也没用了。(Whatever you say是主语从句)
(错)Prisoners have to eat no matter what they‘re given,
(对)Prisoners have to eat whatever they‘re given. 囚犯们只能给什么吃什么。