Final answer:
The two approaches used to study the quantity theory of money are the Classical approach and the Keynesian approach, which are different macroeconomic methodologies to analyze how money supply affects the economy. Monetary policy and fiscal policy are the macroeconomic policies influenced by these approaches. The correct option is c. Classical approach and Keynesian approach.
Step-by-step explanation:
The two approaches used to study the quantity theory of money are c. Classical approach and Keynesian approach. These approaches represent different methodologies within macroeconomics to understand how changes in the money supply affect the economy as a whole. The classical approach is rooted in the idea that the economy is self-correcting, and changes in the money supply only affect nominal variables like prices, but not real variables such as output in the long run. On the other hand, the Keynesian approach suggests that changes in the money supply can have an effect on real output, especially when the economy is not functioning at full capacity and is characterized by price and wage rigidities.
It is important to note that monetary policy and fiscal policy are the two main categories of macroeconomic policy. Monetary policy focuses on regulating the money supply and interest rates, typically administered by a central bank. Fiscal policy deals with government spending, taxes, and borrowing to influence the economy. Both policies can be informed by the Classical or Keynesian approach depending on the economic context or prevailing economic beliefs.
The correct option is c. Classical approach and Keynesian approach.