If the Coefficient a in the New Classical Expression for Short-Run

If the coefficient a in the new classical expression for short-run aggregate supply were equal to zero,

A) aggregate output would always be at its full-employment level.
B) the short-run aggregate supply curve would slope down.
C) the short-run aggregate supply curve would be a horizontal line.
D) aggregate output would only differ from its full-employment level if the actual price level did not equal the expected price level.