Ricardo is famous

David Ricardo is famous for his theory of comparative advantage. This theory states that countries should specialize in the production of goods in which they have a comparative advantage, and then trade with other countries for goods in which they have a comparative disadvantage. This theory is still used today to explain international trade patterns.

Ricardo was also a pioneer in the field of economics. He is considered one of the founders of classical economics, and his work has had a profound influence on the development of economic thought.

Here is a brief explanation of each of the options:

• Population theory: This is the study of how population changes over time. Ricardo was not a major contributor to this field.
• Cost theory: This is the study of how the costs of production vary with the level of output. Ricardo made some important contributions to this field, but his work was later superseded by the work of Alfred Marshall.
• Rent theory: This is the study of how the prices of land and other natural resources are determined. Ricardo made a major contribution to this field with his theory of differential rent.
• Profit theory: This is the study of how the profits of firms are determined. Ricardo did not make a major contribution to this field.