电梯坏了，所以我们不得不爬一段楼梯。

Due to the broken lift, we had to ascend ___a ___flight ___of ___stairs.

他因为让她从一段楼梯上摔下来而自责。

He blamed himself for the accident where she fell down ___a ___flight ___of ___stairs.

有一段螺旋楼梯通向屋顶。

There is a spiral ___flight ___of ___steps leading to the rooftop.