When changes to taxes and spending occur in the economy without explicit action by the central government, such policy is: 
A. Cyclical
B. Variable
C. Discretionary
D. Nondiscretionary

Answer: Non discretionary fiscal policy

Explanation: As the name says these are the policies which are not made on the discretion of the federal Government. The impact of these policies is implemented on the economy automatically, that's why, these are sometimes also referred to as automatic stabilizers.

Progressive taxation during boom times is an example of non discretionary fiscal policy.

Thus, right option is D.