The substitution of steel for wooden ploughs in agricultural production is an example of:

The correct answer is B. Capital-augmenting technological progress improves the quality of the capital good, so each unit of capital gives more productive services. A steel plough is a better tool than a wooden one. It cuts the soil more effectively, lasts longer and needs less repair, so the same stock of implements does more work with the same labour.

• A (labour-augmenting): This raises the efficiency of workers themselves, through education, training, skills or better health. A better tool is not a change in the worker.
• C (capital-reducing): This is not a standard category in growth theory. Capital-augmenting progress is the term used for technical change embodied in capital goods.
• D (None of the above): Wrong, because B fits the case directly.

The concept links to the Solow growth model and to the Hicks and Harrod classification of technical progress. For Mains, it helps explain why mechanisation and better inputs in agriculture raise output per worker and where the returns on capital formation in farming come from.

Trap: Aspirants often pick A because the improved plough seems to make farm labour more productive. Ask first whether the change is in the worker or in the capital good.