let off后面接什么

let off后面接什么？

1.A resident of his neighbourhood had let off fireworks to celebrate the Revolution.他家附近的一个居民燃放了烟花庆祝革命胜利。

2.This train stops to let off passengers on signal.这列火车按信号停车让旅客下车。

3.He let us off homework today.他今天免了我们的家庭作业。