Fifty years ago, bed bugs were nearly eliminated in the United States by using of pesticides like DDT. Today bed bugs are back in beds and theaters. DDT is no longer used due to environmental issues. Pyrethrums are currently the top choice for bed bug infestations. Pyrethrums are especially useful to us because they generally have a stronger effect on bugs than on humans and animals. Some bed bugs had mutations in their genetic code which allowed them to survive the chemical pesticide and they produced chemically resistant offspring. How can this be explained?

A) mutations were planned out by the bugs
B) bed bugs chose other bugs to partner with who had the mutation
C) bed bugs chose other bugs to partner with who had no mutations
D) mutations involved the genetic variation of the bugs are random