In the Keynesian model which includes the Keynesian short-run aggregate supply curve, A. an increase in aggregate demand would causes the price level to rise, but does not change the level of real GDP O B. an increase in aggregate demand causes real GDP and the price level to decrease. O C. an increase in aggregate demand causes real GDP to rise without changing the price level. O D. an increase in aggregate demand changes neither the price level nor the level of real GDP