The correct answer is D. Individual and social choice in the face of scarcity.
Economics is the study of how people make choices under conditions of scarcity. It is a social science that seeks to understand the production, distribution, and consumption of goods and services. Economics also studies the behavior of individuals and businesses in the marketplace.
Option A is about inflation and employment in a growing economy. This is a specific topic within economics, but it is not a general definition of the study of economics.
Option B is about the best way to invest in the stock market. This is another specific topic within economics.
Option C is about business decision-making under foreign competition. This is also a specific topic within economics.
Therefore, the correct answer is D. Individual and social choice in the face of scarcity.