There are several annulenes that are aromatic and consist of many carbons. You may want to take a look at those, they could throw one of those at you I suppose. Just memorize that one (your example), and use what wired said as the rule on the exam.
If the ring has 7 atoms or fewer we can assume that it can adopt a planar conformation. However, if a ring has more than 7 atoms it may or may not be planar. Don't just assume that it's not. Cyclooctatetraene is definitely one to remember that isn't planar though.