她在舞台上绊了一跤，当众出丑。

She ___tripped on stage, embarrassing herself in front of the audience.

他在黑暗中绊了一下，差点摔倒。

He ___tripped in the dark and nearly fell.

我们的计划因意外出现的困难而受阻。

Our plans ___stumbled when unexpected difficulties arose.