请教 og12 86

gmat928

这里有两个帖子

http://forum.chasedream.com/GMAT_SC/thread-352106-1-1.html?SearchText=24%208

http://forum.chasedream.com/GMAT_SC/thread-366299-1-1.html?SearchText=24%208

focusspeed

1）介词（after, before, on）+动名词这个结构通常相当于一个时间状语从句。
2）如果两个动作中有一个在另一个开始之前已经完成，则可以用 after+动名词的完成式表示第1个动作；如果只表示先后顺序，则可用after（或before）+动名词结构； on+动名词通常表示两个动作几乎同时发生：
=>After having been instructed to drive out of town, I began to acquire confidence.
=>The man called the police after being robbed.
=>He killed a child before being arrested.
=>On/After being told that her mother was seriously ill, she hurried back to England.

在google 上搜的，觉得有道理，但也不知道到底是不是正确的，还望大牛指点。