How Would an Economist Use an Aggregate Expenditure Line to Trace

Multiple Choice

How would an economist use an aggregate expenditure line to trace out a single aggregate demand curve?  

A)  by letting changes in autonomous spending shift the aggregate expenditure line 
B)  by letting changes in the price level shift the aggregate expenditure line 
C)  by letting changes in the level of income shift the aggregate expenditure line 
D)  by letting changes in real GDP shift the aggregate expenditure line