停电后，我们不得不在黑暗中爬上十段楼梯。

After the power outage, we had to climb ten ___flights ___of ___stairs in the dark.

她匆忙跑下一段楼梯去应门铃。

She hurried down a ___flight ___of ___stairs to answer the doorbell.

他的公寓在顶层，所以他每天要爬好几段楼梯。

His apartment is on the top floor, so he climbs several ___flights ___of ___stairs every day.