This question asks us to evaluate the significance of a strange savings pattern. This falls a little outside the normal range of GMAT Critical Reasoning problems, but that just means we get to have a little fun figuring it out! Don't get distracted or intimidated when the GMAT throws you a curve ball.

In this case, the argument implies that the pattern might be significant because it stayed steady when we expected it to rise. Why did we expect it to increase? Well, layoffs and unemployment can scare people into savings.

But although layoffs and unemployment can affect savings, so can a whole lot of other things. Even though the question stem was unusual, the actual problem turns out to fit into a classic GMAT argument pattern: unexplored alternatives. In order to determine if the change in savings was truly a mystery of any "significance," we need to know whether any other factors could provide a perfectly mundane explanation. So, our prediction (remember to always predict!) is that the question will be whether or not some other major factor could explain changes in savings.

That leads us straight to (B), which matches perfectly. Note the language in the stem about "discretionary spending," and the reason this is correct becomes clear: if nondiscretionary spending is increasing, savings might stay stable even if discretionary spending is reduced. B is correct.