I don‘t like the course because there is nothing to learn from it.这个it 为什么一定要加?The house is big enough for us to live in.这句句子为什么就不用加it?

I don‘t like the course because there is nothing to learn from it.这个it 为什么一定要加?The house is big enough for us to live in.这句句子为什么就不用加it?
I don‘t like the course because there is nothing to learn from it.
这个it 为什么一定要加?The house is big enough for us to live in.这句句子为什么就不用加it?

I don‘t like the course because there is nothing to learn from it.这个it 为什么一定要加?The house is big enough for us to live in.这句句子为什么就不用加it?
learn from sb/sth to live in是省略句,因为有主语“the house" 故为主语省略!

因为有用from. 所以要写from (where = it = course)
The house is big enough for us to live in 主题明确