Which scenario is an example of irony?

A. Sherry is as fast as a herd of turtles running through peanut butter.

B. Marvin is such a computer genius that he makes Bill Gates look
like a kindergartner.

C. Randy's environmental science project was a large poster of a tree
with a caption that read: "Save the Trees, Go Paperless!"

D. When Trish asked her dad for an advance on her allowance, her
voice was as warm as butter melting on a hot biscuit.