1.动词作主语,开头,用doing
2.介词 in/ at/ for/of /by / about/ with/ without / after/ before + doing
3.swimming club singing class
4.There be …doing (主动)
5.have trouble / problem / fun /…time doing
6.感官动词 see / hear/ notice/ find / feel sb.doing (正在做)
7.practice doing finish doing enjoy doing mind doing spend…(in) doing stop doing(停止做) forget doing(忘了做过某事) remember doing (记得做过某事）
