Final answer:
A series of rulers from a single royal family is termed a dynasty. An oligarchy is a government where a small group of elites hold political power, distinct from a monarchy which is ruled by a single ruler, and a democracy or republic where officials are elected.
Step-by-step explanation:
A series of rulers who come from a single royal family is referred to as a dynasty. This was a particularly important aspect of government in ancient civilizations such as Egypt and China. A dynasty is characterized by a sequence of rulers from the same family, typically where the right to rule is passed down from one generation to the next.
In the context of the different forms of governments presented, a government where a small group of elite people hold political power is known as an oligarchy. Other forms of government discussed include a monarchy, where a single ruler, often a hereditary one, holds the political power, and a republic or a democracy, where officials are elected by the people or represent their interests. Addressing part of a referenced question, modern constitutional monarchies often originated as absolute monarchies, and through a gradual process of constitutional development, have become what they are today.