How does an insect species become resistant to an insecticide?
the more exposure an insect has to the insecticide the weaker the effects of it are.
after an exposure if the insect survives, it mutates to become resistant if it encounters it again.
there are some offspring already resistant to the insecticide's effects that survive and reproduce.
after exposure, all the reproductive cells have mutated to become resistant for the next generation.

C. There are some offspring already resistant to the insecticide's effects that survive and reproduce.

Explanation:

DDT had another negative impact on the environment. In any population, a few flies, mosquitoes, or fleas were not killed by the DDT. They were less sensitive to the chemical. These members of the insect population were the only ones to survive and reproduce. Their offspring inherited the DDT resistant traits. When the area was sprayed again, a few of the less sensitive individuals would again survive and reproduce. With time and repeated spraying, all the insects that were sensitive to DDT had been killed. Only those insects not affected by the DDT remained. This possibility had not been foreseen.

Based on the reading, that's the correct answer.

Edit: Finished the Assignment and yes, this is the Correct Answer.

ill try to . no promises tho.

explanation: