人们可以在路边开店，但必须避免污染。

People can set up roadside businesses but they must avoid pollution.

youdao

但必须是手工操作，而不是在键盘上打字。

But it has to be done by hand, not typing on a keyboard.

youdao

那不是总统的命令所能做到的最好的事情，但必须经过仔细考虑。

That is something not best done by presidential fiat, but only after careful consideration.

youdao

Now, we are very gentle in this course with respect to knowing integrals, but this is one you have to know.

这门课对积分,的要求并不高，但这个积分你们必须会算。

麻省理工公开课 - 热力学与动力学课程节选

I thought I still have to work for another 30, 40 years. I need to do something else.

我原本想，我还必须工作三四十年。但我需要做点别的事情。

怡人的的汉普斯特德 - SpeakingMax英语口语达人

But once you start publishing things in between covers, you actually have to decide what goes in and what goes out.

但一旦你开始把书籍加上封面出版，你就必须决定要出版哪些书。

耶鲁公开课 - 新约课程节选