Kentucky Derby, Preakness, Belmont question

Question
Hi,
Just wondering.. Why are the horses who are in the Kentucky Derby not in the Preakness, except for the winner of course. How do does this all work, even with the belmont.. Hope you can reply or send me a website.  Thank You.. Lynne Thompson

Answer
hi --well, it is always up to the trainer and owners to decide where and when to run their horses next. so ,if the horse did not match up to the  test, then they decide not to run again  against that same quality  horses next time out, and look for a better race that they think they can win.  hope that helps you  thanks ED HESS