Grasslands, such as the prairies of north america,
a. are suitable for corn and wheat, but not suitable for soybeans.
b. are threatened by soil erosion because native grasses have been damaged or destroyed by plowing and overgrazing.
c. support almost no animal life now that the millions of bison that once roamed there are gone.
d. support a rich layer of dense grasses because they receive at least 250 cm (100 in.) of rain per year.