The following options are all reproductive barriers.
which one is an example of a prezygotic barrier in which the two different species do mate?

a. two crayfish species cannot interbreed because their genitalia do not engage properly with each other.
b. hybrid mules produced by mating donkeys and horses are sterile.
c. one bird species lives in wetlands, the other in dry forests; hence, they do not encounter each other.
d. two dragonfly species regularly mate, but their gametes are incompatible.

The answer is B.

Explanation:

A Prezygotic Barrier as a reproductive barrier can be described as the probability of no fertilization from the reproduction of the two species or the result of a sterile offspring that does not have the ability to reproduce.

According to this description, the correct answer is B in which two reproduction of the horse and donkey produce an offspring hybrid mule that does not have the ability to reproduce naturally.

I hope this answer helps.

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.