A Unified Credit Is Subtracted in Calculating Both the Gift

A unified credit is subtracted in calculating both the gift tax and the estate tax. Why doesn't this calculation have the effect of increasing the total unified credit amount?

A) The tentative estate tax is reduced by only taxes payable on adjusted taxable gifts rather than gross gift taxes.
B) The unified credit only offsets the exemption equivalent.
C) The unified credit cannot be used to offset gift taxes on adjusted taxable gifts.
D) The unified credit varies in amount from year to year.
E) None of these