-it might be experimental. Don't stress!
I think people may forget sometimes that there are experimental questions on the actual GMAT exam.
Many of you here have probably read anecdotes of test-takers basically saying that their GMAT was all weird or something unlike anything they saw during their prep. I daresay what some of them probably meant to say was that there was something DURING the exam that was completely weird that they never recovered from, something that they perhaps kept on thinking about. "Gah, I was doing so well until that ruddy question. Ugh, now another one. Seriously?! This wasn't in the OG! I want my money back. What's the point of continuing this now? I lost my target score. $250 down the drain! Great. Now I got that easy one wrong. I just realized. Ugh, what a disaster!"
Long story short, if you see something wonky on the exam, DON'T STRESS! Take a moment and give it a go and think "meh, might have been experimental and won't count anyway" when you click NEXT.
Don't "take" that question forward with you, stressing, becoming irritated and decreasing your focus on the future questions.