参考答案：B

解析：

In an economy that is in equilibrium, the unemployment rate is at the natural rate and the inflation rate is at some long-run equilibrium point. This equilibrium is disturbed when the Federal Reserve considers inflation too high and a policy change is evoked that reduces inflation. In the first case, when the Fed policy change is unexpected by the economy, there will be no discounting or anticipated change in the real wage price by the public prior to the policy change. Thus, when the Fed raises interest rates and slows money growth, aggregate demand decreases. This decline in aggregate demand is not at first fully recognized by the labor markets at the time of the policy change. Wages are not reduced for the lower level of inflation since it is unexpected and wages will remain higher than a full employment level would allow. These higher real wage rates thus reduce demand for labor, arid unemployment rises and results in a recession. In the case of a fully anticipated policy change, the labor market has enough time to adjust real wage rates prior to the actual change in policy. A fully anticipated and credible Federal Reserve change in inflation policy indicates that inflation will be coming down in the near future even though the policy change has not been enacted yet. The real wage rate drops enough for the market to continue to hire the same level of employees as before and keep the natural unemployment rate the same. Thus, a fully anticipated policy change lowers inflation to a greater extent and avoids recession because it allows the markets time to adjust fully to the new equilibrium through real wages in the labor market.