The supposed development is a reduction in spending by people who are still employed, and the expected consequence is unusual growth in those people’s saving accounts. The author concludes that since there’s been no unusual growth, there’s been no reduction in spending.

The author only identifies one predictable consequence of reducing spending—namely, a growth in savings accounts. Also, the conclusion isn’t about whether something is the consequence of a certain behavior—rather, the conclusion is that the behavior itself isn’t occurring.

The author never raises the subjects of economic self-interest, misinformation, error, or economically harmful behavior.

This ignores reasoning by cause-and-effect, which is central to the author’s argument. Instead, (D) describes the following, very different argument: since employed people either did or did not reduce spending, it must be that they did not reduce spending.

The only evidence presented is clear, not ambiguous. The author states, without any ambiguity, that there’s been no unusual increase in the size of employed people’s savings accounts.