a
The two species will likely interbreed with each other, resulting in young with characteristics of both species.
b
The two species will likely interbreed and develop a new species with characteristics of their common ancestor.
c
The two species are no longer able to interbreed and both will continue to exist and reproduce in their separate environments.
d
The two species will be in competition for resources with each other in a single environment, leading to the extinction of one of the species.