Hold the line!
To be fair, we’ve never heard anyone use the phrase “Defend your answer” before. We’ve heard justify, explain, and tell us why you’re allways right, but never defend. With that in mind, we can totally understand why this kid drew what he did.
Anyway, who wants to give a lengthy explanation to an answer that’s already correct or incorrect? The best thing you can do in this situation is make a pun-based meme and hope for the best. In this kid’s case, we hope the “best” was an A on that paper. And that lone stick figure defending the answer deserves a Medal of Honor for his valiant efforts.