Question

there is an equal protection violation when

there is a question of moral servitude.

none of these

the law limits the liberty of all persons to engage in some protected conduct.

the law treats certain classes of people differently from others.

Explanation:

Equal protection violations occur when a law differentiates between classes of people without a valid, constitutionally permissible justification. The other options are incorrect: limiting liberty equally for all does not violate equal protection, moral servitude is unrelated to this legal standard, and the correct option is not "none of these".

Answer:

the law treats certain classes of people differently from others.