The principle of comparative cost advantage was propounded by

Step 1: Analyze the question The question asks who propounded (first put forward) the principle of comparative cost advantage in international trade.

Step 2: Explain the concept Comparative cost advantage means a country should specialize in producing goods for which its opportunity cost is lower than that of other countries, then trade for the rest. Even if one country is better at producing everything (absolute advantage), both countries can still gain from trade if each specializes where its relative efficiency is greatest.

Step 3: Check each option

• A. David Ricardo: He developed the theory of comparative advantage in his 1817 book Principles of Political Economy and Taxation, using the classic example of England and Portugal trading cloth and wine. ✔
• B. Alfred Marshall: Known for supply and demand analysis, consumer surplus, and partial equilibrium. ✘
• C. J. S. Mill: He extended Ricardo's work with the theory of reciprocal demand, but he did not originate comparative cost. ✘
• D. Adam Smith: He propounded the principle of absolute advantage and the division of labour in The Wealth of Nations (1776). ✘

Step 4: Answer The correct option is **A.

Tip: Remember it this way: Smith = Solo (absolute) advantage; Ricardo = Relative (comparative) advantage. Both start with the same letters, which makes it easy to recall in the exam hall.