Explanation:

- Calculation of National Income at Market Prices refers to the sum total of all goods and services produced in a country, valued at current market prices.

- Option 1: Money income – Calculating at market prices means using current monetary values, so this is often termed as "money income". Correct Answer

- Option 2: Real income – This adjusts national income for inflation or changes in price level and reflects the true purchasing power, not directly at market prices.

- Option 3: Non-monetary income – This refers to the value of goods and services not measured in monetary terms (like household work, barter transactions) and is not part of the calculation at market prices.

- Option 4: None of these – This is incorrect as Option 1 is correct.