Q: There are two reasons why. I like baseball. It is fun. And good exercise.

A: There are two reasons why I like baseball, it is fun and good exercise.

Is this correct?

3 answers

No.

You have two separate sentences which could be separated by a semicolon.
There are two reasons why I like baseball; it is fun and good exercise.

Is that what you mean?
Yes. It's now correct.