What Were So-Called Bonanza Farms That Spread Across the Country

What were so-called bonanza farms that spread across the country during the second half of the nineteenth century?

A) farms that were fertilized using new chemical compounds developed in labs
B) farms that were fortunate enough to have large deposits of oil discovered on them
C) farming communities established in Kansas by African American migrants from the South
D) socialist farming collectives established in unorganized western territories
E) corporate-owned farms that were run like factories