A change in A. Government purchases would cause the aggregate demand curve to shift.
Aggregate demand is influenced by the total spending in the economy, which includes consumer spending, investment spending, government purchases, and net exports. Changes in government purchases directly affect aggregate demand because increased government spending raises overall demand, shifting the aggregate demand curve to the right. Conversely, a decrease in government spending would shift the curve to the left.
Changes in productivity, wages, and resource availability primarily affect aggregate supply rather than aggregate demand.