When a Small Subset of a Larger Population Gets Separated

When a small subset of a larger population gets separated into a different environment from the main population, which of the following is likely to occur

A) The new small population will have a different set of traits and may experience different environmental conditions than the larger one and so will evolve differently.
B) The new small population will eventually regain all the traits of the original large population by natural selection.
C) Since the original population will always be better adapted, the new population is likely to die off.
D) Since the new population will eventually be better adapted as a result of experiencing a new environment, they will eventually overtake the original population.
E) Nothing will happen since the new, isolated population is unlikely to survive.