When Only Synthetic Fertilizers Are Used on a Crop, the Quantity

Multiple Choice

When only synthetic fertilizers are used on a crop, the quantity used needs to be increased over time because ________.

A) they are washed away by seasonal rains, but residual fertilizers remain
B) organisms in the soil develop a resistance to these fertilizers
C) more and more genetically engineered crops are being planted
D) synthetic fertilizers provide no organic bulk