专家们注意到“教科书是有层次的，就像洋葱一样”。对于主动学习者来说，接触课本是一种具有互动性的体验。

Experts observe that "textbooks come in layers, something like an onion". For an active learner, engaging with a textbook can be an interactive experience.

youdao

那是因为核电站是成层的，就像洋葱。

That's because nuclear power plants come in layers, like an onion.

youdao

50后，他们就像洋葱。

After 50, they are like Onions.

youdao

It seems like the moment you begin to look at this question, you were just like peeling the onion.

感觉你们在看待这个,问题时，就像剥洋葱一样。

普林斯顿公开课 - 人性课程节选