Awoman treated her home with a pesticide that kills spiders. the first application killed 78% of the spiders. two months later she applied the pesticide again, but it only killed 45% of the spiders. what would best explain the decrease in the effectiveness of the pesticide?
a. the pesticide only works on mature spiders.
b. once spiders learned how to avoid the pesticide they taught others.
c. the surviving spiders were naturally resistant to the pesticide and that resistance was inherited by their offspring.
d. some of the spiders became able to digest the pesticide due to mutation of the digestive tract.

Option C, the surviving spiders were naturally resistant to the pesticide and that resistance was inherited by their offspring.

Explanation:

As per the Darwin's theory, the fittest of all survive and hence the spiders that were the fittest at the time of first application of pesticide survived. Being fittest means that they have learned how to survive in an environment consisting of pesticide/or were naturally resistant to the pesticide.

After the first interaction with pesticide,  the remaining spiders evolved further with course of time to resist the effect of pesticide. Now when these evolved spiders reproduced, the new born individuals had inbuilt resistance to the similar type of pesticide. This is the reason why only 45 percent spiders died during the application of pesticide for the second time.

Option C is correct.