The "right" answer

One portion of Dondan's homework asked for the shaded portion of a prism:


I had to help him with this because "HIS" answer was NOT one of the choices.
Dondan: "Mom NONE of them is the right answer!"
Mom: "Okay, then what IS the right answer?"
Dondan: "It's a parallelogram Mom."
I would have to agree with him on that, but after much deliberation and convincing we concluded the answer was rectangle.
I was rather impressed, I didn't know he even knew what a parallelogram was.
Go Dondan.