Answer: A. the state of being the most powerful
Step-by-step explanation:
Supremacy is the state of being the most powerful. It simply means having the highest authority and limitless power.
Option B is incorrect as the intentional and organized killing of a group of people based on their ethnicity, race, religion, nationality, or other trait is refered to as genocide.
Option C is incorrect as the extension of power of one nation over another, often by territorial acquisition is refered to as imperialism.
Option D is incorrect as the devotion to ones country isn't supremacy.
Therefore, the correct option is A.