Which of the people or institutions listed exercises the most power over the quantity of money in the United States economy?

In the long run, firms in many industries often experience falling average total costs as a result of

a. gains through trade. b. increasing marginal returns. c. economies of scale. d. lower fixed costs.

Someone notices that sunspot activity is high just prior to recessions and concludes that sunspots cause recessions. This person has:

A. confused association and causation. B. misunderstood the Ceteris paribus assumption. C. used normative economics to answer a positive question. D. built an untestable model.