一旦发生紧急情况，我一定会为祖国献身的。

I will offer myself to the state as an emergency arises.

youdao

请让汤姆通知谢菲尔德，他可能需要他们的代班（机器人），以防下星期发生紧急情况。

Please ask Tom to inform Sheffield that he may need their stand-ins in case of emergency during the next week.

youdao

一旦发生紧急情况，打电话给警察。

In case of urgency, call the police.

《新英汉大辞典》