Three populations of crickets look very similar, but the males have courtship songs that sound different. What function would this difference in song likely serve if the populations came in contact?

A) a behavioral reproductive isolating mechanism

B) a temporal reproductive isolating mechanism

C) a gametic reproductive isolating mechanism

D) a postzygotic isolating mechanism

Answer is A. a behavioral reproductive isolating mechanism.

Explanation:

A behavioral isolation mechanism can be described or explained as a mechanism whereby, mating rituals or signals of species of an organism are different from one another, in order to prevent interbreeding or interest in courtship among them.

In this case, the organisms in the population may be similar, and have the tendency of interbreeding, but, because of their different mating or courtship signals, the interbreeding won't be possible.