Answer:
b. supply; demand
Explanation:
Before Keynes, classical economists thought that aggregate supply was more important than aggregate demand in determining the overall economic level of a country. This was mainly because of the belief in say's law: the law stated that every offer creates its own deamand.
Keynes changed economics because he stated that demand and supply do not always reach equilibrium, and that demand is often insufficient, and it is the government job to stimulate demand through expansionary monetary and fiscal policy, like lowering interest rates and cutting taxes.
