Question

If bed bugs had never been exposed to DDT in the 1950's and 1960's, how would you expect that to affect bed bugs' resistance to pyrethroids during the last decade?

Answer 1

its D: Without the use of DDT, natural selection would not have favored any mutations that provided protection from pesticides; bed bugs would be more susceptible to today's chemicals.

Answer 2

What is the connection between DDT and pyrethroids? They are both pesticides, but different ones. However, many mutations that protect the bugs from one of them also work on the other.

So, if they had been exposed, they'd be selected for resistence to these pesticides. But if they have not been exposed; they would be dying more often during the last decade.