Which of the following economic reasoning behind the twin deficit theory is not correct? a. According to the national income accounting, if private saving and investment stay constant, a government budget deficit can cause a trade deficit by reducing national saving. b. Government budget deficits (due to expansionary fiscal policy) and trade deficits during the 1980s and early 2000s in the US are the cases of the twin deficits. c. The chain of causality can work in a reverse way: a smaller fiscal deficit leads to a smaller trade deficit, other things being equal. d. All of the above are correct