Explanation:

- Market economy is a system where economic agents can freely exchange their endowments with each other. Supply and demand determine prices, and the government has minimal intervention.

- Centrally planned economy is characterized by the government making all decisions about the production and distribution of resources. Individuals have little control over what they produce or consume.

- Aggregate demand based economy focuses on total demand within the economy, but it is not a standalone type of economic structure.

- Aggregate supply based economy is centered on the total supply but similarly isn't a standalone type of economic structure.

- Answer: Market economy is correct as it fits the description given.