For Centuries Before Europeans Arrived on the North American Continent

For centuries before Europeans arrived on the North American continent, Native Americans prevented the encroachment of forests farther west and maintained the tallgrass prairies throughout the area that now includes Missouri, Iowa, and Illinois by:

A) clear-cutting the forests for timber and fuel.
B) establishing an extensive irrigation system to increase soil moisture, thus favoring grasses.
C) plowing much of the land for agriculture.
D) restricting the migrations of bison, which caused them to browse heavily on tree seedlings and thus killed them.
E) setting fires periodically to kill the trees.