Explanation:

- Option 1: Wholesale price index

- It measures the average change in prices at the wholesale level.

- It's more of a macroeconomic indicator as it deals with the economy as a whole.

- Option 2: National income

- It refers to the total income earned by a nation’s people.

- This is a macroeconomic variable, reflecting the economy's overall performance.

- Option 3: Market demand

- It represents the total demand for a product by all consumers in a market.

- Market demand is a microeconomic variable as it focuses on individual markets.

- Option 4: Aggregate demand

- It is the total demand for all goods and services in an economy.

- This is clearly a macroeconomic concept.