Question

a farmer has used pesticides on corn crops that have been selected for plumpness for many years. the farmer encounters pests after treating his corn crops this past year. which best explains the presence of the pests?
pests become genetically resistant.
pests washed away the pesticide.
the pesticide was mixed incorrectly.
there was an increase in the pest population.

Explanation:

When pesticides are used repeatedly, natural selection occurs. Pests that have a genetic mutation for resistance are more likely to survive and reproduce. Over time, the proportion of resistant pests in the population increases. This is an example of how environmental pressure (pesticide use) leads to the evolution of a trait (pesticide resistance) in a population.

Answer:

Pests become genetically resistant.