Congress passed the Civil Service Reform Act in 1989

The fact that the United States has different tax rates for different levels of income relates to which of the following phrases?

a. Politics is "the master science." b. The Constitution is "the crown jewel of the Enlightenment." c. "Man is by nature a political animal." d. Politics is the study of "who gets what."

The ________ preserved peace among the great powers throughout the nineteenth century by creating a more multilateral and open system for settling disputes.

Fill in the blank(s) with the appropriate word(s).