Answer:
A. Balance of Power
Step-by-step explanation:
Balance of power deals with international politics and power sharing among the nations. It refers to relative power position of states as actors in international relations.
Congress of Vienna which held during 1814-15 , after the fall of Napolean Bonaparte , the European power blocks like Britain , Austria , Russia , etc. began to discuss the power equation and measures to further limit the wars and losses. It helped to shape the future developments related to military and defence of the nations in comparison to other neighbours.