What was the social structure in each of the civilizations?

There was four main classes that consisted of Brahmins which were priests and the king, Kshatriyas which were warriors and aristocrats (rulers), Vaishyas which were artisans and merchants, and finally Shudras which were peasants and serfs. There was another class under the Shudras called the Pariahs.

Explanation:

the answer would be c. sediment buildup on continental slope

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