Government Expenditures and Taxes Are Assumed to Be Autonomous

Government expenditures and taxes are assumed to be autonomous.What does this mean?  

A)  Government expenditures and taxes do NOT depend up on the level of GDP. 
B)  Government expenditures and taxes may be changed only through direct action by Parliament. 
C)  Government expenditures and taxes change only when the price level changes. 
D)  Government expenditures and taxes are autonomous at low levels of GDP but NOT at higher levels of GDP.