So it's very important to be keeping in mind that any time you see a double bond, you have a pi bond there, so you're not going to see any rotation around the bond axis.

所以你们要记住,任何时候你们看到一个双键，这里面有π键，你们不会看到关于键轴的任何转动。

麻省理工公开课 - 化学原理课程节选

Isn't it difficult being a mother and a professor at the same time and keeping a balance between the two?

同时做母亲和教授是不是很困难呢？两者之间取得平衡不容易吧？

教授的梦想 - SpeakingMax英语口语达人

It's actually better to spend a certain amount of time just keeping your body in good condition

其实花一定时间保持身体的良好状态更好，

健康生活 - SpeakingMax英语口语达人