Explanation:

- Option 1: National Income

- Macro economics studies national income. It's the total value of goods and services produced by a country.

- It reflects how the economy is doing overall.

- Option 2: Full Employment

- Full employment is another aspect of macro economics.

- It aims to ensure that all who are willing and able to work can find a job.

- Option 3: Total Production

- Total production in an economy is a macroeconomic concern.

- It looks at the aggregate output of goods and services.

- Option 4: All of these

- Macro economics indeed studies all of the above aspects.

- It focuses on the economy as a whole.

- All of these options fall under macroeconomic study.