What were the main divisions of Inca society? How did members of an ayllu help one another?

The Inca society was a vertical hierarchical organization divided in four social classes. At the top of the stratum was the Sapa Inca, the most powerful person in the empire. Below was the royalty, comprised by the sons of the Sapa Inca and his close relatives. The third social class was the nobility which included royal relatives and those who attained distinction through their services such as priests and chiefs. At the bottom of the pyramidal social structure was the ayllu which included the majority of the population.

Ayllu workers gathering potatoes as part of their mita work

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Society in the Andes was built around the ayllu. All its members had some kind of family ties, like an extended family. They all believed they were descendants of a common ancestor. The head of the ayllu was the caraca. The ayllu was also the base of economic activity. Ayllu members worked the land and took care of the cattle for food and clothing, and they worked in the mines or as weavers. They were all obliged to work and contribute to the mita or tax. In exchange the Inca would secure food throughout the year, provide agricultural products not produced in the area, education and health care.

this question does't support enough resioning to answer.

the correct answer is c.