What made the Adena groups unique?

A. They built mounds over graves and sites used for special events.

B. They were the most advanced farmers among the early cultures.

C. They were the first to build mounds over graves in clear geometric shapes.

D. They would grind rocks to make axes and tools for processing food.



Answer :

Final answer:

The Adena groups were unique for building mounds over graves and sites used for special events.


Explanation:

The Adena groups were unique for building mounds over graves and sites used for special events. These mounds started small with the burial of important people, but grew over time. Structures and evidence of postholes found in some mounds suggest ceremonial purposes as well.


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