eroding the land by tilling overproducing food crops removing weeds from crops spraying plants with pesticides
I gave my students this multiple choice question: By inserting a gene into crop plants, scientists have developed plants that are resistant to insects. If an insect eats the plant, the insect dies. Which practice is unnecessary with this new plant variety?

Only one answer is correct among these 4 choices:
- eroding the land by tilling
- overproducing food crops
- removing weeds from crops
- spraying plants with pesticides

Could you tell me which one is correct?

spraying plants with pesticides