Which of the following is true? a. Economics is the study of the choices we make among our many wants...

Which of the following is true? a. Economics is the study of the choices we make among our many wants and desires, given our scarce resources. b. In a world of scarcity, our unlimited wants exceed our limited resources. c. Rational behavior involves doing the best you can, based on your values and information, under current and anticipated future circumstances. d. Choices are costly because they require that we must give up other opportunities that we value. e. All of the above are true.