这就是问题的关键所在。

This is the crux of the matter.

《新英汉大辞典》

肥胖是这一问题的关键所在。

Obesity is a key part of the big picture.

youdao

谈判中适当施压是解决问题的关键所在。

The pressure part of this equation is crucial.

youdao

Does it really matter to you whether your code is going to take 300 years or 900 years to run?

或者900年区别大么？,这个数字的规模才是问题关键所在？

麻省理工公开课 - 计算机科学及编程导论课程节选

So if you know the answer and know what the fix is don't answer this.

如果知道答案,知道问题的关键所在，先不要说出来。

哈佛公开课 - 计算机科学课程节选