Do ALL 20 year old kids know EVERYTHING?

The real estate class I survived this week consisted of adults, most of whom were 28+. However, I found myself next to a lanky kid who reminded me of my 20 year old grandson. I asked him how old he was. He’ll be 20 this year.
I said, “Do you have a bad attitude?” kind of laughing.
He kind of snapped, “NO!” I thought…“uh oh!”
Then I said, “Do you know everything?”
He just looked at me with disdain.
As the class went on he did, as it turned out, know everything. He knew more than anyone else in the class, and he let everyone know it.
Of course, he didn’t know shit but everyone tolerated it because he’s a kid.

Did you know everything at 20? I have a bad feeling that I did! Trying to remember it though. It was a while back.