In a mixture of oil and water, what are the oil and the water called?

Only things with atomic numbers are elements... a mixture of oil and water is called an emulsion. Consequently, this must be a trick question. The only help is using the process of elimination -- it can't be "A" nor "B" and certainly not "C", so it's gotta be "D". I can see where these two substances could be in a process of changing phases.