The correct answer is A. Oligarchy.
An oligarchy is a form of government in which a small group of people hold power. This group may be made up of wealthy individuals, members of a particular social class, or military leaders. Oligarchies are often characterized by corruption and a lack of accountability.
A monarchy is a form of government in which a single person, the monarch, holds all or most of the power. Monarchies can be hereditary, meaning that the title of monarch is passed down from one generation to the next, or they can be elective, meaning that the monarch is chosen by the people or by a group of nobles.
A democracy is a form of government in which the people hold power. This can be done through direct democracy, in which the people vote on laws and policies directly, or through representative democracy, in which the people elect representatives to make decisions on their behalf.
Anarchy is a state of disorder and lawlessness. In an anarchist society, there is no government and no one is in charge.