Answer: B. Males of different, closely related species of fireflies signal for mates by flashing different light sequences.
Reproductive isolation refers to the inability of the members of a species to breed with members of other species. Behavioral isolation is a type of reproductive isolation, in which mating between the members of the species is facilitated by their behavior. It helps members of the same species to identity their mates. It prevents mating between population of distinct species.
Males of different, closely related species of fireflies signal for mates by flashing different light sequences is an example of behavioral isolation because flashing of light by fireflies is the behavioral characteristic which shows their desire for mating. The mates identify the light signals flashed by their partner belonging to the same species.