1.在进行时态中。如：

He is watching TV in the room.

They were dancing at nine o'clock last night.

2.在 there be结构中。如：

There is a boy swimming in the river.

3.在 have fun/ problems/ difficulty结构中。如：

We have fun learning English this term.

They had problems getting to the top of the mountain.

We have difficulty (in) learning English.

4.在介词后面。如：

Thanks for helping me.

Are you good at playing basketball.

5.在以下结构中： enjoy doing sth乐于做某事; finish doing sth完成做某事; feel like doing sth想要做某事; stop doing sth停

止做某事; forget doing sth忘记做过某事; go on doing sth继续做某事; remember doing sth记得做过某事; like doing sth喜欢做

某事; keep sb doing sth使某人一直做某事; find sb doing sth发现某人做某事; try doing sth试图做某事; need doing sth需要做

某事; prefer doing sth宁愿做某事; mind doing sth介意做某; practice doing sth练习做某事; be busy doing sth忙于做某

事; can't help doing sth禁不住做某事; miss doing sth错过做某事; see/ hear/ watch sb doing sth看到/听到/观看某人做某事