A Group Is Experimenting with Selection in an Insect Species

A group is experimenting with selection in an insect species due to exposure to a newly developed insecticide, cpd AW143. The group has found that after 10 generations of exposure, the population is now bimodal in its response to the drug. Close to 30% of the population are completely normal while 70% live only about 1/6 of the normal lifetime. This is an example of __________.

A) threshold effect
B) stabilizing selection
C) additive genes
D) directional selection
E) disruptive selection