Final answer:
The correct answer is option 3. An increase in interest rates will have the smallest expansionary effect on aggregate demand in the short run.
Step-by-step explanation:
In this case, an increase in interest rates will have the smallest expansionary effect on aggregate demand in the short run.
- Increasing government spending will directly increase aggregate demand as the government's spending injects money into the economy.
- A decrease in taxes will increase disposable income, leading to higher consumer spending, which will boost aggregate demand.
- However, an increase in interest rates will discourage borrowing and reduce both consumer spending and investment spending, resulting in a smaller expansionary effect on aggregate demand.
- A decrease in consumer spending, while it may reduce aggregate demand, will still have a larger effect than a change in interest rates.
Therefore, among the given options, an increase in interest rates will have the smallest expansionary effect on aggregate demand in the short run.