Which of the following is a correct statement? A. Economic concepts or laws that are valid during depression are necessarily valid during prosperity. B. Although they are generalizations, economic laws are useful because they allow us to predict and therefore control or adjust to events. C. Economics is as scientific as are physics and chemistry because economic laws are as quantitatively precise as the laws of physics or chemistry. D. Because economics is concerned with questions of "ought," it is a branch of applied ethics and not scientific.