We know that the average age increased from approximately 52 to 57 years - that's a fact. We want to strengthen that people over 65 have drastically increased. Well, choice (A) at first might seem counterproductive to that, because wouldn't that pull the average down? Not necessarily.
We know that the average age went up, so if people 18 or younger increased, it has to be the case that older people (i.e. people over 65) went up even higher to move this average up, not down.
AllisonJon June 18, 2021
Thank you, this really helped a lot, and now this make so much sense.