洞是无形的，就如人不会是十全十美，我们或许永远填不满这洞，就好像人不会十全十美，也就正如学习，学习是无止境的。

The hole is intangible, as people are not perfect, we may never fill the hole, as if people do not perfect, also like learning, learning is endless.

youdao

人的生命是有限的，但学习知识永无止境。

Our life is limited, but knowledge is boundless.

youdao