If Employees and Employers Always Accurately Forecast Inflation,what Is the Shape

Multiple Choice

If employees and employers always accurately forecast inflation,what is the shape of the Phillips curve?

A) It is upward sloping in the short run, and horizontal in the long run.
B) It is vertical in the short run, and upward sloping in the long run.
C) It is vertical in the short run and in the long run.
D) It is downward sloping in the short run, and vertical in the long run.