Q.Who among the following defined Economics as "the science of wealth"?

Each of the four classical economists linked to this chapter is remembered for one signature definition of Economics.

Adam Smith, in An Inquiry into the Nature and Causes of the Wealth of Nations (1776), defined Economics as the science of wealth, concerned with the production, exchange and distribution of a nation's wealth. Option (a), Alfred Marshall, instead defined Economics as the study of mankind's material well-being (the welfare definition) — wealth was a means, not the subject itself, for Marshall. Option (c), Lionel Robbins, rejected the wealth idea altogether and defined Economics as the science of choice between scarce means and unlimited ends — his definition never mentions wealth. Option (d), Paul Samuelson, gave the later growth-oriented definition, which does discuss production of commodities but frames it around resource allocation over time, not wealth as such. Only Smith's definition is built specifically and solely around the idea of wealth, which is why (b) is correct and the other three are incorrect.

Students sometimes confuse Smith's wealth definition with Marshall's welfare definition, since both are 18th/19th-century classical views — the key test is whether wealth is treated as the end (Smith) or only a means to well-being (Marshall).