In the Short Run, When Will Real and Nominal GDP

Multiple Choice

In the short run, when will real and nominal GDP both decrease?
 

A)  whenever aggregate demand decreases, but NOT always when aggregate supply decreases 
B)  whenever aggregate supply decreases, but NOT always when aggregate demand decreases 
C)  whenever aggregate demand decreases or aggregate supply decreases 
D)  whenever aggregate supply decreases along a constant aggregate demand curve