A) As long as the Fed's announcement is credible, workers and firms will increase their consumption and investment spending, which will increase aggregate demand and inflation.
B) As long as the Fed's announcement is credible, workers and firms will decrease their consumption and investment spending, which will decrease aggregate demand and inflation.
C) Workers and firms will incorporate the decrease in interest rates into their expectations of inflation, and they will expect inflation to fall as a result of Fed's policy announcement.
D) If the Fed's announcement is not credible, workers and firms will not expect inflation to rise so they will increase their consumption and investment spending, which will decrease aggregate demand and increase inflation.