Referring to a keynesian phillips curve, a reduction in inflation is likely to cause: at least a slight increase in aggregate demand. a vertical phillips curve because aggregate supply remains fixed. unemployment to remain constant in the long run. at least a slight increase in unemployment.

I think the correct answer is the last option. Referring to a Keynesian Phillips curve, a reduction in inflation is likely to cause at least a slight increase in unemployment. A Phillips curve shows relation between inflation and unemployment. In this curve, inflation and unemployment are inversely proportional which means that as the inflation rises, the unemployment would decrease. The opposite of such event is also true.