They spend their lives studying their subjects and know what's possible and what is not.

他们用毕生精力去研究他们的课题，知道什么是可能的，什么是不可能的。

youdao

So in other words, if I say what's the partial pressure of CS2, well, since it's not the simple ideal case, actually I don't know what it is in general.

那么换句话说，如果我说CS2的分压是什么，由于它不是简单的理想情况，事实上我不知道它通常是什么。

youdao

It's important that you stay "in the know" about what's happening in the job market, what industries are getting coverage, and what's "hot" (and more importantly... what's not).

重要的是：你要始终知道就业市场上发生了什么，哪些行业被报导了，什么是“热点”(更重要的是……哪些不热门了)。

youdao

Some people might not have firm plans yet for New Year's Eve, but others know exactly what they will be doing.

VOA: special.2009.12.28

Usually when you know why it's not working, it's obvious what you have to do to make it work.

通常你明白了出错的原因后，很明显你必须让程序正常运行起来。

麻省理工公开课 - 计算机科学及编程导论课程节选

So, if we have a high intensity, we're talking about having more photons per second, and it's important to know also what that does not mean.

所以，如果我们有一个高强度，我们就是在讨论每秒钟,有更多的光子数，同样理解它不代表什么,也是很重要的。

麻省理工公开课 - 化学原理课程节选

"It's hard to know what's bluster and what's not with the Israelis, " said a former U.S. official.

WSJ: U.S. Warns Israel Against Iran Strike

Third, we urged states to use cutting-edge data systems to track a child's progress throughout their academic career, and to link that child's progress to their teachers so we know what's working and what's not working in the classroom.

WHITEHOUSE: Race to the Top for Education Reform

Mr. VARTHAM HAVAKIAN (Student, Lebanon): When you have the police censor your text, you don't know what is accepted and what is not, so that's our problem.

NPR: Play Challenges Lebanese to Face Past, Present