A large population of cockroaches was sprayed with an insecticide. A few of the cockroaches survived and produced a population of cockroaches that was resistant to this spray. What can best be inferred from this example?
A A species will adapt no matter what the environment.
B The environment has no effect on the survival of an organism.
C Insecticides cause mutations that are passed on to the next generation.
D Individuals with favorable variations survive and reproduce.