NO-BOOK口语提高版 Lesson110:背后
文本：
Lesson 1 Behind
is behind this?
2.I'm behind you.one hundred percent.
't burn your bridges behind you.
're still wet behind the ears.
's behind in handing in the paper.
6.I slipped and fell on my behind.
did you do this behind my back?
e must be something behind this.