Based on the graph, which of the following would cause the aggregate demand $($AD$)$ curve to decrease from AD$2$ to AD$1?$

a$.$ There is an increase in the price of oil.

b$.$ The economy has been producing more than its full$-$employment output level, and wages and input prices begin to rise.

c$.$ There is a reduction in income tax rates.

d$.$ There is a reduction in consumer confidence about future growth in the economy.

e$.$ There is an increase in the general price level that reduces real wealth.