A population of rhinos was separated by a large river. Since rhinos are lousy swimmers, they were unable to cross. Environmental conditions were very different on either side of the river, and over time these two groups of rhinos evolved such different characteristics that scientists classified them as two
different species. This is an example of:

A. sympatric speciation

B. homologous speciation.

C. analogous speciation

D. parapatric speciation

E. allopatric speciation