Answer:
C. In the long run, aggregate supply is vertical.
Explanation:
Phillips curve: A curve showing the short-run relationship between the unemployment rate and the inflation rate. It says when inflation is high, unemployment tends to be low; when inflation is low, unemployment tends to be high. The short-run Phillips curve exhibits a a trade-off between inflation and unemployment, whereas in the long-run Phillips curve does not, as in the long run it become unrelated. Therefore, ploting both curve on graph, it will show phillips curve is vertical at the natural rate of unemployment.