Look at the four squares, [A], [B], [C], [D], which indicate where the following sentence could be added to the passage. Where would the sentence best fit? Today, however, the original grassland associations of plants and animals have been almost completely destroyed by human settlement. [2] One hundred years ago, the Great Plains grasslands were vast, unbroken prairie. [A]Much of the prairie is now farmland, the most productive agricultural region in the world, dominated by monocultures of cereal grains. [B]Wheat, barley, soybeans, corn, and sunflowers occupy the land that was once prairie. [C]In areas given over to grazing lands for cattle and sheep, virtually all the major native grasses have been replaced by alien species. [D]