depleting the ozone layer burning gasoline in car engines throwing trash out of car windows allowing runoff from agricultural fields
I gave my students this multiple choice question: Which human activity directly affects the quality of freshwater resources?

Only one answer is correct among these 4 choices:
- depleting the ozone layer
- burning gasoline in car engines
- throwing trash out of car windows
- allowing runoff from agricultural fields

Could you tell me which one is correct?

allowing runoff from agricultural fields