This answer to me has nothing to do with the argument, to me, it does not strengthen it either.

Hi Tyler808, Strengthen and weaken questions are a little odd in that the correct answer can seem fairly distant from the argument, as long as it strengthens or weakens it. The argument is telling us that there has been an increase in old people, as shown by a rise in the average age. However, there are two ways an average could rise- perhaps there are more old people, or perhaps there are fewer young people. A closes off the possibility that the rise in the average came from a fall in the number of young people. It strengthens the argument by rebutting a possible argument against it. This is a valid way to strengthen an argument, by fixing a flaw in the argument.