Pls help me answer this question and pls put an explanation

Afor ram b for pats super bowl pick one

Which of the following can occur to two segments of a population if they are geographically isolated 1.) they can only share some types of genes 2.)both groups most likely become extinct 3.)they find a way to come back together 4.)eventually they become separate species

What type of cell division is used to replace old cell?