left off的用法和樣例：
例句
用作形容詞 (adj.)
- You'll save electricity by turning off lights not in use.
把不用的燈關(guān)掉能省電。 - So many people had those beepers attached to their belts and they took great care to expose them even when not in use,just to show off.
好多人把它別在腰帶上，不用的時(shí)候也想方設法把它露出來(lái)，就是為了炫耀。
