Which human activity had the biggest impact on dust storms in 1930 a. diverting rivers and streams b. using industrial pollutants c. replacing natural grasses with crops d. settling in new areas

ANSWER:

Replacing natural grasses with crops had the biggest impact on dust storms in 1930.

EXPLANATION:

Farming had been extensively practiced in 1930s. The farmers ploughed the fields and grew a wide variety of crops that replaced the natural grasses. The natural grasses had the ability to keep the soil fixed and trapped not allowing it to be carried away easily by water or wind. The removal of natural grasses led to the erosion of the top-soil which eventually led to dust storms and massive destruction.

Answer:   [b]:   "cultural" .