decreasing soil fertility decreasing oil transportation increasing the greenhouse effect increasing carbon dioxide emissions
I gave my students this multiple choice question: Corn is widely being used in the United States to make ethanol for use in automobile fuel. How might the overproduction of corn negatively affect the environment?

Only one answer is correct among these 4 choices:
- decreasing soil fertility
- decreasing oil transportation
- increasing the greenhouse effect
- increasing carbon dioxide emissions

Could you tell me which one is correct?

decreasing soil fertility