Genetic modification makes plants more resistant to killer weeds. However, this can lead to environmental damage by
Explanation:
In the last paragraph the author states: “farmers use massive dosages of weed-killers so as to destroy or wipe out all competing varieties of plants in their fields. However, some weeds through genetically modified pollen contamination may acquire resistance to a variety of weed-killers. The only way to destroy these weeds is through the use of ever-stronger herbicides, which are poisonous and linger on in the environment.” This idea is illustrated in option 2. Soil fertility has not been mentioned in this regard (option 4 can be eliminated). The herbicides cause the damage and not the plants (option 1 eliminated). Option 3 does not adequately explain the reason for environmental damage.
Hence, the correct answer is option 2.