First of all, I'd like to state that a lot of you are morons.
I'm sorry if this offends any of you, but you should really READ EVERYTHING before you post a reply.
YES it has been pointed out a MILLION TIMES that kids can't come up with things like pressure, or atmospheric compounds.
It MUST be a simple answer if 84% of kindergarten children can guess the answer within 6 minutes (and yes, I know that the statistics could quite possibly be made up for the purpose of the riddle)
Think for a minute. Kindergarten children are generally aged 4-6 years old. They've only just started learning.
Sorry, I know this will disappoint a lot of you, but the answer isn't QUANTUM BIOMECHANICAL PARADIMETHYLAMINOBENZALDEHYDE PRESSURISATION.
Just think. If kindergarten kids can answer it, then it isn't that hard. But I still get the feeling someone will post after me with another new stroke of genius that yet again seems like way too complex of an answer for a young child to come up with.
Personally, I think the more probable answer is a negative reply, such as "No"
I know that when I was in kindergarten, it was hard enough to colour in between the lines, nevermind staying concentrated for long enough to figure out a riddle.