Which native american group is known for having build huge earthen structures in the mississippi river region

The  Cahokia Mounds People

Explanation:

These ancient Indians built more than 120 earthen mounds in the city, 109 of which have been recorded and 68 of which are preserved within the site. Many others are thought to have been altered or destroyed by farming and construction. While some are no more than a gentle rise on the land, others reach 100 feet into the sky.

Mound Builders

Explanation:

The first people entered Mississippi many years ago. The earliest phase mounded construction in the area. However, the mounding continued in the later years. According to the scientist studying the evidence of past human life, the Indian molding was done in three different phases. However, in the modern days brought worked mounds have not been traced.

The mold construction, however, was been declined by the Europeans when they invaded the region in the 1500s. This was after the break down of epidemic disease that affected the natives causing societal disruption.

answer; i believe the correct answer is (crops);

explanation:

allergens: overstimulate the nerve system

neurotics: attack nerve cells

mutagens: damage or otherwise alter dna sequence

generators: cause defects during growth and development  

carcinogens: cause unchecked cell growth

i hope you get the idea according to me these are the effects that happened.