Aspecies is a group of organisms capable of mating and producing offspring, and speciation is the process of forming a new species

one way a new species may form is by isolation. this occurs when members of a population are physically separated, for example, by a river, or a desert.

The answer is geographic because once the species separate they may evolve differently creating new species.

geographical isolation

Explanation:

one way a new species ma form is by geographical isolation.

Geographical isolation is a form of reproductive isolation in which a physical barrier separates two population of similar species. Each population then go on to become a new species.

Reproductive isolation itself is a mechanism of speciation in which organisms are prevented from producing offspring through mating or produce an invalid offspring if mating and fertilization cannot be prevented from taking place.

When two population of the same species become geographically isolated, each population will follow different evolution path and then become new species.

cells spend most of their time in interphase