他一直在同一个词上结巴。

He kept ___stumbling over the same word.

紧张的新星在表演时开始结巴，说不顺台词。

The nervous new star began to ___stumble over her lines during the performance.

即使是最有经验的演讲者，在面对突发的技术故障时也可能会支吾。

Even the most seasoned speaker can ___stumble when faced with a sudden technical glitch.