The correct answer is: C. deals with the tools of economics used for decision making in business.
Business economics is a field of study that applies the principles of economics to business decision-making. It is concerned with the allocation of scarce resources in order to maximize profits or minimize costs. Business economists use economic models and theories to analyze market conditions, identify opportunities, and make sound business decisions.
Option A is incorrect because business economics does not study economic relationships in general. It focuses on the application of economic principles to business decision-making.
Option B is incorrect because business economics does not study economic activities at the aggregate level. It focuses on the individual firm or industry level.
Option D is incorrect because business economics does not study optimum allocation of limited resources in general. It focuses on the application of economic principles to business decision-making.