In Which of the Following Ways Was Cyrus McCormick's Grain

Multiple Choice

In which of the following ways was Cyrus McCormick's grain reaper significant?

A) It transformed the economy of the South.
B) It required farmers to rely more on muscle power than ever before.
C) It was powered by gasoline engines rather than horses.
D) It helped bring mechanical power to the Midwest, Old Northwest, and Great Plains.
E) It had to be assembled by farmers.