Who holds state power in an oligarchy? a single person the representatives of the people the people themselves a small group of people

The answer is: a small group of people

An oligarchal system has government run by a few powerful citizens or families. This minority depending on the extent can rule over a land, kingdom, empire, or nation. An oligarchy is a form of power structure in which power rests with a small number of people ( it has some similarities to a monopoly, and is contrary to a representative democracy). These people may be distinguished by nobility, wealth, family ties, education or corporate, religious or political, military control. We can see many examples of oligarchy in today's world although the term is also associated to a concept used to refer to criticism of the current state of things (when we hear the term putative oligarchies. it is often referred to countries like Russian Federation, Ukraine or even The United States. As we can read:

Putative oligarchies

refer to: "A business group might be defined as an oligarch if it satisfies the following conditions:

(1) owners are the largest private owners in the country (2) it possesses sufficient political power to promote its own interests (3) owners control multiple businesses, which intensively coordinate their activities