Question

Two organisms can be considered to be of different species if they

-live in two different geographical areas
-cannot mate with each other and produce fertile offspring
-mutate at different rates
-have genes from the same gene pool

Answer 1

organisms belong to the same species if they can interbreed to produce viable, fertile offspring. Species are separated from one another by prezygotic and postzygotic barriers, which prevent mating or the production of viable, fertile offspring.

I would say the second one.

Answer 2

the second one, is the most reasonable one.

definitely not the last one.