Which two sentences best describe the effects of the agreements at the Congress of Vienna?

A and D.

Explanation:

The Congress of Vienna was an international meeting held in Vienna aimed to restore peace and structure in Europe. The meeting was held from November 1814 to June 1815. The Great Powers (Great Britain, Russia, Prussia, and Austria) came together to plan for the postwar world. After the end of Napoleon war, the Great Powers started making decisions on how to restore the power and monarchy that were overthrown by Napoleon.
The two statements that describes the effect of the Congress of Vienna are A and D.
France's political power was weakened by the Great Powers. France had to return the territories that it gained during Napoleon war.
Another aim of the Congress of Vienna was to bring balance of power. Balance of power is a political theory according to which military support were distributed as such that no state becomes stronger than other. In case if one state becomes stronger and threaten other countries then those weak nations were given power to unite against the stronger one.

So, the correct answer is option A and D.