Concept:The principle of comparative cost advantage explains why countries benefit from trade by specialising in goods they can produce at a lower relative opportunity cost.
Explanation:David Ricardo propounded this principle in his 1817 work
On the Principles of Political Economy and Taxation.
He showed that trade is beneficial even when one country produces every good more efficiently than another.
Each country should specialise in the good where its cost disadvantage is least, or its cost advantage is greatest.
This is different from Adam Smith’s theory of absolute advantage.
Alfred Marshall and J.S. Mill did not introduce this principle.
Thus, the correct economist is David Ricardo.
Answer:A. David Ricardo