of Macroeconomics Spring 20 fall20 Economic activity moves from a period of expansion to a until it reaches a and then moves into a period of Select one: O a trough; expansion; peak O b. peak, recession; trough O c. trough; recession; peak O d. peak; expansion; trough Next page to search O a op is $ % & of Macroeconomics Spring20 fall20 Which of the following is not one of the reasons why it is difficult to empirically test alternative macroeconomic models against one another? Select one: O a. The amount of data available is fairly small. O b. The rational-expectations assumption is difficult to test. O c. Macroeconomic models cannot be expressed in mathematical terms. O d. Macroeconomic models differ in ways that are hard to standardize for. Next pag search O a hp