The correct answer is D) a single ruler.
The other options of the question were A) a tricameral legislature B) rule by all people C) tyranny of the majority over other views
While an oligarchy is a society ruled by a small class of politically, economically, or socially empowered people, by contrast, a monarchy involves a single ruler.
In a monarchy, the king is the absolute ruler of the kingdom. The best examples were the kings of Europe during the dark age of the Middle Ages. There were powerful kings that exerted total power and control over their reigns. During most of these years, people lived under the oppression of the king. Just noble people or landlords were welcomed in the king's court.