DDT is a synthetic compound commonly used as an insecticide. It was used to control mosquito species that commonly spread diseases like malaria. The data show the percent resistance for three species of mosquitoes over three decades. What explains the trend seen in the data

The phenomenon that explains the trend seen in the data is that the mosquitoes' evolution has led them to develop resistance to the compound.

Explanation:

This is a very common factor that we can see in insects. The effect of DDT on the species will have different levels of impact. One is going to be more vulnerable to the compound that the rest. However, after many times of exposition to the compound, a few survivors will develop resistance to the compound and their offspring is going to inherit that resistance. Making them increase the resistance over time.

i am going to guess that it is co2.