Answer:
b. founder effect
Step-by-step explanation:
When there is a situation when sufficient number of members of one species are reproductively isolated, and if there is an evolutionary pressure for them to start developing new advantageous traits, then a new species will gradually emerge. In this kind of scenario the genetic diversity will be minimized, as the number of individuals is much smaller, and that will result in only changes that will go in only one direction and they will also occur quicker than if there was a greater genetic diversity. This is called the founder effect, and it is easy to see why this term has been chosen, as the limited number of members of a species that have been reproductively isolated are giving the foundation for the development of a new, separate species.