Answer:
Reproductive isolation is a system of barrier that does not allow different species or even similar species to mate. The example of behavioral isolation is shown by fireflies in which males flash light in different sequences to attract females. So the answer is 'D'.
Step-by-step explanation:
Species have trouble in mating with each other so easily. Certain reproductive barriers are placed by the nature which do not allow them to mate. These barriers are classified as prezygotic and postzygotic.
In prezygotic, the process of mating does not occur and in case of postzygotic the organism formed is incapable of surviving. Behavioral isolation is a type of prezygotic barrier. In this the behavior of individuals like mating rituals and signals are very specific for organisms to reproduce. For example in case of some birds, dancing is a way to attract females but all males dance differently. In case of fireflies, the males emit different pattern of light sequences and females select the best pattern they like.