The adena, hopewell, and mississippian native american cultures were known for

Building Mounds

Explanation:

The mound builder cultures of North America, are best known for their capacity to build mounds which are relics from their societies that were found in several places, the names of this native american tribes are given by where they found relics from them, because no one of these survived the 18th century. They build different kind of mounds :

animals like bears, snakes and birds.

Giant cones and flat pyramids.

Walls of earth on the central midwest.

the answer is b.

hope this !

it refers to race, i am pretty sure this was a popular term in nazi germany or something.