after doing s.th还是after do s.th?在书上看到两句话:1、After listening to it2、After they listen to it为什么一个是 doing s.th 一个是do s.th?

问题描述:

after doing s.th还是after do s.th?
在书上看到两句话:
1、After listening to it
2、After they listen to it
为什么一个是 doing s.th 一个是do s.th?