If a Population of a Single Species Gets Split into Two

If a population of a single species gets split into two different environments, and each environment requires different traits for survival, what might happen over time?

A) The population in each environment would evolve differently to suit the conditions and might eventually become two distinct species.
B) The populations in each environment would evolve differently to suit the conditions and would compete and eventually one would win and the other would go extinct.
C) Both populations would progressively get bigger to fit the new environment.
D) One population would tend to mutate more than the other, by chance, and so would evolve into a new species.
E) Individuals would tend to mutate to fit the different conditions, eventually leading to two separate species.