Final answer:
Discretionary fiscal policy's primary aim is to adjust the level of aggregate demand to stabilize the economy, aligning real GDP with potential GDP. Therefore correct option is B
Step-by-step explanation:
Discretionary fiscal policy is a tool used by the government to regulate the economy's level of activity. It involves deliberate changes in taxation and government spending to influence aggregate demand. The goal of such policy can be either to increase economic output when the economy is underperforming (expansionary fiscal policy) or to cool down the economy when it is overperforming (contractionary fiscal policy).
Option (a) relates to policies designed to increase long-term economic capacity or Potential GDP, which isn't the primary domain of discretionary fiscal policy. Rather, options (b) to shift the aggregate demand curve so that real GDP equals potential GDP, and (c) to shift the aggregate supply curve to the right are more directly aligned with the intentions of discretionary fiscal policy. Option (d) to reduce unemployment further when it's already at a low level could potentially overstimulate the economy and lead to inflation.
However, the most accurate description of discretionary fiscal policy's aim would be to adjust the level of aggregate demand to achieve economic stability. Therefore, the correct choice is (b) shift the aggregate demand curve so that real GDP equals potential GDP. Such shifts help in addressing cyclical fluctuations and maintaining the equilibrium between potential output and actual economic performance.