It's CoRnY
A kid can joke but a joke cannot kid.
Because it wasn't recycled.
An Envelope EDIT: My deepest Canadian apologies to those who are calling this a riddle. I always took it as a cheesy joke
It was asbestos they could do at the time!
The corner.
Because they're too high-strung. Corny I know, but I wrote it myself and had to put it out there.
Barium, Cobalt and Nitrogen.
