Can you elaborate why do you think so? I'm not asking for correct answer on this question of course (indeed if candidate would answer correctly it means that he knew the answer and the question had no point). I'm expecting to confuse candidate by providing him correct answer and then ask him to find out why his assumption differs from correct answer. This is common in software development and observing how does one tries to understand wrong code provides valuable insight on his skills.
Another question that I like is asking to find out issues in one fragment of code. This fragment is crafted to contain style issues, some bugs and architecture issues. This allows to understand the level of candidate: which issues can he spot. Not ideal, but I think it works good enough.
I think the assumption was that you were asking for the correct answer. Definitely makes sense after you explained it though (at least, it makes sense to me.)