In their attempts to bring the invasive rabbit population under control, Australian authorities have utilized biological rabbit-killing viruses. However, this solution presents a number of problems. One is that the sudden, widespread deaths can put predator populations in danger. Another is that a growing proportion of the rabbit population becomes virus-resistant as the rabbits naturally resistant to a particular virus survive to breed.

Assuming that they are realistic possibilities, which of the following would be a way to extend the effectiveness of using biological rabbit-killing viruses?


(A) Using only biologically stable viruses
(B) Periodically switching to different rabbit-killing viruses
(C) Gradually increasing the virulence of the viruses used
(D) Leaving certain rabbit populations alone for a few years
(E) Breeding rabbits with lower fecundity

[spoiler]OA is B. For me this choice address the second problem only (resistance to the virus). That why I took D that address the first problem as well (to save predators since at least part of the rabbits will be available for them). Where is my flaw?[/spoiler]