The correct answer is: a) Feudal hierarchy.
A feudal hierarchy is a system of government in which a small number of powerful people, called lords, control land and resources, and a larger number of people, called peasants, work the land and provide services to the lords in exchange for protection and a share of the crops.
The Aka (Hrusso) chiefs in West Kameng maintained a form of feudal hierarchy. The chiefs were the most powerful people in the community, and they controlled the land and resources. The peasants worked the land and provided services to the chiefs in exchange for protection and a share of the crops.
The other options are incorrect. Option b) is incorrect because a cooperative tribal council is a system of government in which a group of people make decisions together. Option c) is incorrect because direct British control is a system of government in which the British government directly controls a territory. Option d) is incorrect because a centralized monarchy is a system of government in which a single person, the monarch, has absolute power.