Correct Answer: Sales revenue earned by a firm

Solution : The correct answer is (d) Sales revenue earned by a firm

Sales revenue earned by a firm is not included in the calculation of national income. National income refers to the total income earned by individuals and entities within an economy. While sales revenue represents the total amount of money generated from the sales of goods or services by a firm, it does not directly contribute to national income. National income includes components such as wages, salaries, rent, interest, and profits, but not sales revenue.