Option 1 -> Measures GDP by calculating the total value of goods and services produced in the economy.
Option 2 -> Measures GDP by summing all expenditures (Consumption + Investment + Government Spending + Net Exports).
Option 3 -> Measures GDP by adding all factor payments like wages, rent, interest, and profits earned by factors of production.
Option 4 -> This is an inventory valuation method, not a method for measuring national income.
Hence, Option 3: Income Method -> The Income Method calculates national income by summing all factor payments made to the factors of production. Factor payments include wages and salaries (to labor), rent (to land), interest (to capital), and profits (to entrepreneurs). This method focuses on the income earned by all factors in the production process, making it the correct answer -> correct