Macroeconomics is the study of A. why the U.S. has spent so much money on wars and government surveillance of its own citizens. B. how households and firms make​ choices, how they interact in​ markets, and how the government attempts to influence their choices. C. the economy on a​ state-by-state basis, covering areas affected by the Commerce Clause. D. the economy as a​ whole, including topics such as​ inflation, unemployment, and economic growth.