Final answer:
The Keynesian model assumes that aggregate demand is crucial for economic activity and advocates for government intervention through fiscal policy. It also assumes the presence of wage and price rigidities.
Step-by-step explanation:
The Keynesian model assumes that aggregate demand plays a key role in determining the level of economic activity. It emphasizes the importance of government intervention through fiscal policy, such as increasing government spending or decreasing taxes, to stimulate demand and fight recessions. The model also assumes the existence of wage and price rigidities, meaning that wages and prices do not adjust quickly to changes in demand or supply.