It’s that “Oh” I can relate to. Exasperation. Wornoutness. That sense of falling into a vat of sticky cotton. That feeling I get from many of the conversations between me and my youngest dear one.
“Mommy, what happens when we eat too many trees?”
“Humans don’t eat trees. Unless they’re very, very hungry.”
“But what happens if we do?”
“Um… we get a sore throat?”
“Why do we get a sore throat?”
“All those branches must be scratchy.”
“No, Mommy, listen to my words. What. Happens. When. We. Eat. Too. Many. Trees.”
“Um… we get a bellyache.”
“MOMMY! YOU ARE NOT LISTENING! LOOK AT ME!”
“Honey, I can’t look at you, I’m driving.”
“MOMMY! LOOK! AT! ME!”
“Barnaby, if I look at you we’ll crash into those cars ahead of us!”
<A heavenly six seconds of silence during which I stress about looming deadlines – not a good use of rare quiet time.>
“Mommy, what will happen if we crash into those cars ahead of us?”
“We will all die a horrible death.”
“Why will we all die a horrible death?”
“We. Just. Will.”
<A heavenly six seconds of silence during which I ponder the wisdom of talking about horrible deaths with a three year old.>
“Mommy, what will happen if we eat too many cars?”
And repeat. And repeat. And repeat.
Let us go then, you and I 
Oh, my! Did this one take me back. Jeff’s question couldn’t be answered. I never thought I would forget the exact wording, but I have. Write ’em down. It was something like – Why is blue? He wasn’t asking why something was colored blue, or what made up blue, or why does color exist. Three year old brains are amazing. Thanks again for a phenomenal post.