Species a has a breeding call that is completely different from species b. this difference in breeding call leads to
a. prezygotic isolation
b. postzygotic isolation
c. coevolution
d. sympatric speciation

The correct answer is option a.

Explanation:

Prezygotic isolation is a mechanism by which mating and fertilization is prevented. Thus, it prevents the formation of a zygote.

It can be achieved by various reasons such as temporal differences (difference in mating seasons), habitat isolation, behavioural differences (different mating rituals such as different dance patterns, voice calls, et cetera), mechanical isolation, et cetera.

Thus, different breeding calls prevent the species to interbreed with each which ultimately prevent the formation of zygote formation.

Hence, it is a type of prezygotic isolation.