A Trade-Off Between Aggregate Output and Inflation

Multiple Choice

A trade-off between aggregate output and inflation

A) is theoretically possible, but has never been observed in practice.
B) may exist in the short run, but not in the long run.
C) exists in both the short run and the long run.
D) is part of the Keynesian sticky wage model.
E) may exist in the long run, but not in the short run.