In National- Income Accounting, "Double Counting

In national- income accounting, "double counting"

A) leads to an underestimation of GDP in any given period.
B) means that consumption will always be less than GDP.
C) means that pre- tax and after- tax GDP will be different.
D) occurs when the value of output is counted more than once in the calculation of national income.
E) occurs when the value of some output is omitted in the calculation of national income.