The Phillips Curve shifts over time because: O a. inflation expectations adjust. O b. unemployment is always equal to its natural rate. O c. the long-run aggregate supply curve shifts. O d. policymakers can pick any inflation rate they like. Policymakers incorrectly believed, based on the Phillips Curve, that: Ofa. in the long run, the unemployment rate would be equal to its natural rate. O b. the tradeoff between inflation and unemployment changed over time. O c there was a short-run tradeoff between inflation and unemployment. O d. they could achieve a given unemployment rate by setting the corresponding inflation rate. Why is it easier for people to upgrade their houses when there is demand-side inflation than it is for people to downgrade their houses when there is demand-side deflation? O a. Because during deflation, they may not be able to sell their current house more than they owe O b. Because during inflation, they may not be able to sell their current house for more than they owe O c. Because during deflation, construction companies may be too busy to build newer, smaller houses O d. Because during inflation, they may not have enough assets to qualify for a new mortgage