Abilities and Evolution

How do abilities carry over when the lowest form, as well as the higher forms, have multiple abilities to choose from? Is it like, if you get ability 1, and you evolve, you get ability 1 of the evolved form? Or does it randomly select the ability of the evolution.

Here's my personal example, for which I am asking.
Corsola: Has Hustle and Natural Cure.
Corsoreef: Has Sharp Coral and Natural Cure

If I wanted Sharp Coral, would I have to raise a Corsola w/ Hustle? Or would it just be a 50-50?

Hustle becomes sharp coral. It's like ability 1 stays ability, same with ability 2