What Does Double Counting in the Value-Added Approach to GDP

What does double counting in the value-added approach to GDP refer to?  

A)  corporate income being taxed twice 
B)  calculating GDP twice using the income method and the expenditure method 
C)  adding the value of exports to GDP and subtracting the value of imports 
D)  counting the total value of a final output in addition to the value of the inputs used to make it