Joke Collection Website - Talk about mood - How to make use of the early knowledge, and why make sentences at the beginning?

How to make use of the early knowledge, and why make sentences at the beginning?

1、? If I know this, why should I know it? What you say now is of little practical significance.

2、? He regretted it only after he failed in the senior high school entrance examination. If I know this, why should I know it? !

If I know this, why should I know it? You asked for these things.