How can you determine what a liquid above a precipitate is?

Question

I have a question on a homework that asks about what a water layer above a precipitate is?

I know it's probably depending on what chemicals are used, but how can i determine what that liquid is?

It gives a hint that states:

"Remember that ionic compounds are electrolytes and dissociate when dissolved in water. Polyatomic ions remain intact."

Answer 1

The liquid part is also called the supernitant

Answer 2

When you mix AB and CD they will dissociate into A+, B-, C+ and D-. So, if AD forms a precipitate, the liquid will contain CB in its dissolved form of C+ and B-.

The question isn't very clear but I guess that is your answer.