Explanation:

- Net National Income at Factor Cost refers to the total income earned by a country’s factors of production (labor, capital, etc.) minus depreciation and indirect taxes, plus subsidies.

- Option 1: National Income

- Correct Answer

- It represents the total value of a nation's final goods and services produced during a given year.

- Option 2: Gross Investment

- This is the total amount spent on new capital and replacing depreciated assets, not related to Net National Income.

- Option 3: Domestic Income

- It typically refers to the income generated within a country, but it’s usually calculated before indirect taxes and subsidies.

- Option 4: None of these

- If no options were relevant, but Option 1 is indeed relevant here.