Answer:
D. real business cycle models.
Step-by-step explanation:
The theory of real business cycles explains short-run economic fluctuations based on the assumptions of the classical theory. Real business-cycle (or RBC theory) is a class of new classical macroeconomics models in which business-cycle fluctuations to a large extent can be accounted for by real shocks.
According to this theory, business cycles are the natural and efficient response of the economy to economic environment. Contrary to what Keynesian, Monetarist, and new classical economicsts believed, RBC theorists, starting with Nelson and Plosser in 1982, found that the hypothesis that GDP growth follows a random walk cannot be rejected. They argued that most of the changes in GDP were permanent, and that output growth would not revert to an underlying trend following a shock.