Using the aggregate demand and aggregate supply model, a decrease of what curve is by itself consistent with the changes in prices and output that occurred during the onset of the great depression?

The correct answer is aggregate demand.

Explanation:

On the onset of the great depression, the stock market crash led to a reduction in consumer confidence. As a result, the investment in capital market declined. This caused the aggregate demand curve to shift to the left. This further caused nominal wages to increase. As a result, the aggregate supply increased.  

The reduction in wealth affected the consumer confidence adversely causing a further reduction in consumption and thus decline in aggregate demand. When the government revenue declined due to a fall in income and consumption, the governments increased tax rates to compensate. Higher taxes further led to a fall in disposable income causing consumption and aggregate demand to decline.

The rightward shift in the aggregate supply curve because of a fall in nominal wages failed to increase real GDP because of continuous reduction in aggregate demand.

d is the best answer for this question.