他在黑暗中被玩具绊了一下差点摔倒。

He ___stumbled over a toy in the dark and almost fell.

她在回答问题时有些结巴，显然很紧张。

She ___stumbled over her words when answering the question, clearly nervous.

我在整理房间时意外发现了一张老照片。

I ___stumbled across an old photo while cleaning the room.