Answer: Option B.
Two population separated by missippi river.
Step-by-step explanation:
Allopatric speciation occur when two populations of the same species become isolated from each other due to geographical changes.
Allopatric species are unable to interbreed due to geographical separation.
Two populations separated by missippi river is an example of allopatric speciation. The populations are geographical separated and the river is the barrier making them not to be able to interbreed with each other.