The correct option is A
speciation
Origin of new species from the existing one is called speciation. Geographical and reproductive isolation are an important factor in formation of new species, when environmental conditions change or migrate to a new area. Speciation requires that the two incipient species be unable to produce viable offspring together or that they avoid mating with members of the other group.
The environment may impose an external barrier to reproduction, such as a river or mountain range, between two incipient species but that external barrier alone will not make them separate, full-fledged species.
Allopatry may start the process off, but the evolution of internal (i.e., genetically-based) barriers to gene flow is necessary for speciation to be complete.
Extinction is the dying out or extermination of a species.
Succession is the process that describes how the structure of a biological community (that is, an interacting group of various species in a desert, forest, grassland, marine environment, and so on) changes over time.
Competition is a term that describes how living organisms directly or indirectly seek resources. Competition can occur within a species or between different species.
So the correct answer is "option a".