Answer: D. geographic isolation and reproductive isolation
Speciation can be defined as a evolutionary process by which a new species develop from a parent species. It occurs when the members of the species becomes reproductively isolated and physically get separated due to geographical barriers. In allopatric speciation, the ancestral population evolve into a new species due to geographical barriers like river which separate the two populations of the same species apart. In sympatric speciation, the ancestral population evolve into a new species due to the reproductive and behavioral isolation. This is due to the fact that the members of the two species becomes incapable of inbreeding.