In the late 19th century, the invention of the first gasoline-powered tractor allowed farmers to grow more wheat on the Great Plains. What did this farming innovation contribute to? A. an increase in the buffalo population, as it made more food available for them to graze on B: the elimination of the Plains Indians, as their land was taken over by farmers C. the expansion of slavery, as more free labor was needed on the larger farms D. an obesity pandemic as most Americans now. had a surplus of food to eat