Do you remember your first exam to join the school?

I don't remember it clearly, because my first exam was like one of my dreams. Later my teacher told me how it was.

Well, it was a simple sum: On the pool there was 7 ducks, 3 of them sunk. How much ducks remained.

And what do you think, which my answer was?
"WHY THEY SUNK?" - Yeah, it was my answer on their sum!