When a single species evolves into two species, the new species must

be reproductively isolated.

evolve different diets.

be exposed to the same selective pressures.

live on a different continent.

Be reproductively isolated

Explanation:

According to the Biological concept of species, organisms can be considered a species when it can interbreed to produce a fertile and viable offspring and cannot reproduce with the organism of another group

If the organism will not reproduce with an organism of another group it means that they are reproductively isolated and reproductive isolation is the main characteristic of the biological species.

In the given question, if the species are evolved to form a new species it means that they must be reproductively isolated and no longer reproduce.

Thus, the selected option is correct.