Answer:
Behavioral isolation.
Step-by-step explanation:
SInce the example is saying that both species of frogs are in the same area, this eliminates the option of geographical and habitat isolation, since they are already togheter and have similar diet, appearence and DNA this means they could interbreed, and since the example is not saying anything about breeding times for each species, we can not assume this is a temporal isolation, so the only thing that sets them apart is the fact that they have different breeding rituals, since one species breeds on water ponds and the other in fast-moving streams, this is known as Behavioral Isolation, since it´s their breeding rituals that keeps them from interbreeding.