D. for which the demand mercuses 38) Whenever one variable increases another variable decreases. The two variables are definitely related through a third variable. negatively related. C. positively related. D. unrelated to each other. The study of the choices made by individuals is part of the definition of microeconomics. B. positive economics. C. macroeconomics D. normative economics. results in an increase in the demand for a product? A fall in the price of the product.B. A smaller number of consumers wanting to buy the product. An increase in the price of the product D. An increase in the price of a substitute product.