re: 1 door closes, 9 open riddle... are you refering to the one by the Queen of Sheba? and if so, her riddle is kind of odd and icky at the same time... I don't get how all of them are opened or closed... I won't go into details. You can look it up for yourself. It's referenced in the Bible : book of Kings.
Initially, this was a great idea... hope you post a riddle as often as you like.
Re: the riddle...
The answer is for you to choose from countless modalities of logic, and within your own belief systems. All possible answers are fun (I like the 9 lives answer quite alot), however only one "right" answer using emprical logic prevails.
Your Hint: You could spend the rest of your Life enjoying solving the riddle ;)
Now Let's buy More C, My Fellow Respected Peers, and Teabag some Shorts, eh?
Have A Great Day & Good Trading~