Answer:
a) allopatric speciation
Step-by-step explanation:
Allopatric speciation occurs when two populations of a species are separated by a geographical barrier. This geographical barrier, which can be a mountain, desert or forest, for example, causes a spatial separation (allopatry). In this case, we say that a geographic isolation occurred.
When these populations separate, they may undergo different pressures as they are in different areas. These pressures, over time, cause a genetic divergence and, consequently, a possible reproductive isolation. Many consider this type of speciation as the main model of speciation.