Final answer:
A decrease in aggregate demand may be caused by d. a decrease in business optimism about the future.
Step-by-step explanation:
A decrease in aggregate demand may be caused by a decrease in business optimism about the future. When businesses are less optimistic about the future, they may reduce their investment and production, leading to a decrease in aggregate demand. This can have a negative impact on the overall economy.
For example, if businesses believe that there will be a decrease in consumer demand for their products in the future, they may reduce their investment in new production facilities and equipment, leading to a decrease in aggregate demand. Additionally, businesses may decrease their hiring and lay off workers, further reducing consumer spending and aggregate demand.
Therefore, a decrease in business optimism about the future can be a significant factor in causing a decrease in aggregate demand.