他在黑暗的走廊里绊了一下，差点摔倒。

He ___stumbles in the dark hallway and almost falls.

她在面试时紧张得说话结结巴巴。

She ___stumbles through her words when nervous during the interview.

她在清理阁楼时意外发现了一箱旧照片。

She ___stumbles across a box of old photos while cleaning the attic.