Explanation:

- Factor income: This includes wages, rent, interest, and profits earned through the use of factors of production. It's part of national income.

- Rent: Earnings from land or property. It’s included as it contributes to the productive process.

- Operating surplus: Profits earned by businesses after subtracting labor costs. It is part of national income calculation.

- Transfer income: This includes all sorts of income that are not earned through economic activity, like pensions, unemployment benefits, or remittances. It’s not included in national income as it is not a result of productive activity.

Correct Answer: Transfer income