The Common Edible Frog of Europe Is a Hybrid Between

The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when they mate among themselves, they are rarely successful in producing offspring. What can you infer from this information?

A) Postzygotic isolation exists between the two frog species.
B) Prezygotic isolation exists between the two frog species.
C) These two species are likely in the process of fusing back into one species.
D) The hybrids form a separate species under the biological species concept.