All right, turn them off. If they have to make noise as you turn them off, turn them off, but that's it. So, when you walk through that door, it's an act of free will.

好了，把它们关掉，如果一定要发出声音,当关机的时候，也要关机，就这样，当你走进那扇门，这是自由意志的选择。

麻省理工公开课 - 固态化学导论课程节选

Make sure you fasten your safety belts.

一定要系好安全带。

Make sure 课堂 - SpeakingMax英语口语达人

You've got to look after yourself.

你一定要照顾好自己。

have to 课堂 - SpeakingMax英语口语达人