In which process do ionic compounds separate into their oppositely charged constituent ions when they are dissolved in water?
a.) dissociation
b.) electrolyte
c.) hydration
d.) ionization

Option (A) is the correct answer.

Explanation:

When an ionic compound is dissolved in water then the compound readily  dissociates into ions. This process is known as dissociation.

Whereas an electrolyte is a solution that contains ions and it is able to conduct electricity.

Hydration is a process in which a molecule or compound is chemically  attached to water molecules.

On the other hand, ionization is a process in which a molecule is able to acquire positive or negative charge.

Thus, we can conclude that in dissociation process ionic compounds separate into their oppositely charged constituent ions when they are dissolved in water.

nacl is added to the aqueous of what? ? in order to get a proper answer you have to specify the exact composition of the aqueous solution.