Some Resource Prices Are Assumed to Be Constant in the Short

Multiple Choice

Some resource prices are assumed to be constant in the short run.How does this affect the shape of the short-run aggregate supply curve?  

A)  The aggregate supply curve is horizontal in the short run. 
B)  The aggregate supply curve is vertical in the short run. 
C)  The aggregate supply curve slopes upward in the short run. 
D)  The aggregate supply curve slopes downward in the short run.