The Northern leopard frog (Rana pipiens)and Southern leopard frog (Rana utricularia)are morphologically similar,but have undergone behavioral isolation.Based on this,what is the most likely reason they are considered separate species?

A)The Northern species breeds during spring,while the Southern species breeds in late summer.
B)The mating calls of the two species are different.
C)Adults of the Southern species are entirely terrestrial,while adults of the Northern species are entirely aquatiC.
D)Hybrids of the two species are sterile.
E)Sperm of the Northern species are unable to penetrate the membrane of eggs of the Southern species.