- 20 Introduction to irregular verbs _ The parts of speech _ Grammar _ Khan Academy 视频 0 次下载
- 21 The funky -ed irregular verb _ The parts of speech _ Grammar _ Khan Academy 视频 0 次下载
- 23 The irregular verb gets taken for a ride _ Grammar _ Khan Academy 视频 0 次下载
- 24 The truly irregular verbs _ The parts of speech _ Grammar _ Khan Academy 视频 0 次下载
- 25 Introduction to verb aspect _ The parts of speech _ Grammar _ Khan Academy 视频 0 次下载