Our immune system's function is to keep us healthy in the face of an environment where there are lots of things that could potentially harm us.

我们免疫系统的功能就是保持自身健康,在面对危机四伏的环境时,使我们免受伤害

耶鲁公开课 - 生物医学工程探索课程节选

you're the face, you're the person who's supposed to keep the troop, you know, the, the rank and file motivated.

你是球队的标志，是保持球队战斗力和激情的主心骨。

足球部队长的领导力 - SpeakingMax英语口语达人