He bombed the exam.
By looking at a bomb
Dinomite!!!!! *budum tssst*
Chen says, "it is because I have forgotten her name"
YOU SAID YOU'D NEVER FORGET!
Bromate Sorry, just studying my poly atomic ions and thought I was clever. I thought wrong
A HISSSSStorian.
Too many cheetahs
Billy's Mom asked him, "Well, why aren't you studying, Billy? You have an exam tomorrow!" Billy said, "Because I've already Reddit thrice."
A Tryptophanatic.
Allah them. (I googled several varations and thus far I believe I am the originator)