Answer:
it is the sovereign nation-states
Explanation:
A sovereign nation-state is a government body defined by a centralized administration
If you have any questions feel free to ask in the comments. - Mark
An oligarchy- by definition- means, “A small group of people having control of a country, group, or organization.” (Source for definition: “Google”)
The answers not supported by this definition are: B, C, and D, as B and C are citizen-contributed systems, and D is a monarchy/dictatorship.
This leaves us with answer “A” being the only plausible answer to fit our description.
I hope this helps!
Answer: it's A or B
Explanation: the rest don't make any sense