他紧张地摸索着纽扣，怎么也扣不上。

He ___fumbled with the buttons, unable to fasten them properly.

他在比赛关键时刻失手掉了球。

He ___fumbled the ball at the critical moment of the game.

他在面试中结结巴巴，回答问题时显得很紧张。

He ___fumbled during the interview, nervously answering the questions.