Don’t forget to the lights before you leave the classroom.A. turn on B. turn off C. turn u

问题补充：

Don’t forget to the lights before you leave the classroom.

A. turn on B. turn off C. turn up

答案：

解析：turn on 打开，发动；turn off 关闭；turn up出现，开大。句意：在你离开教室之前，不要忘了关点灯。结合语境可知选Ｂ。