regret to do 对要做的事遗憾。 (未做)
regret doing 对做过的事遗憾、后悔。 (已做)
I regret to have to do this, but I have no choice.
I don't regret telling her what I thought.
---You were brave enough to raise objections at the meeting.
---Well, now I regret ___ that.
A. to do B. to be doing C. to have done D. having done
答案：D。regret having done sth. 对已发生的事感到遗憾。regret to do sth. 对将要做的事感到遗憾。本题为对已说的话感到后悔，因此选D。
try to do 努力，企图做某事。
try doing 试验，试着做某事。
You must try to be more careful.
I tried gardening but didn't succeed.
go on to do 做了一件事后，接着做另一件事。
go on doing 继续做原来做的事。
After he had finished his maths，he went on to do his physics.
Go on doing the other exercise after you have finished this one.
cease to do 长时间，甚至永远停做某事。
cease doing 短时停止做某事，以后还会接着做。
That department has ceased to exist forever.
The girls ceased chatting for a moment when their teacher passed by.
mean to do 打算、想
mean doing 意味着
I mean to go, but my father would not allow me to.
To raise wage means increasing purchasing power.