다음 글의 빈곳에 적절한 것은?
strong people make as many mistakes as weak people.
the difference is that theformer admit them,laugh at them and learn from them.
that is________________.

1.what they became strong
2.that they became weak
3.how they became strong
4.to think that they bacame weak
5.what they learn from others

기초적인거 알지만 영어 독학 하려니 힘드네요
답은 3번인데 왜 3번인지모르겠네요..
be동사 뒤에 명사 형용사올수있는건아는데..
알려주세요 ㅠㅠ