Hello everybody. I'd like to know the reason why this picture was rejected.

We cannot say it often enough. View your photos at a minimum of 100%!. I think 200% to 300% is even better. 

If you did, you should have seen these artifacts.

Also your photo is a bit too noisy in the sky and the shadows are way too underexposed.

This is what the proper exposure shows.

The reviewers gave you a rejection reason.  I assume it was for technical issues. 

The foreground is too dark and the sky is washed out in places.