Some farmers rotate their crops from year to year, switching from soybeans to corn on the same fields. What is one of the advantages of doing this?
(a) Soybeans add large amounts of carbon dioxide to the soil, which helps the corn crop.
(b) Both crops require the same fertilizing supplies, so farmers save by buying fertilizer in bulk.
(c) Corn adds large amounts of phosphorus to the soil, which helps the soybean crop
(d) The corn crop benefits from reactive nitrogen added to the soil by the soybean crop