text: You can think of the formation of the gas giants as mini-nebular events like the one the formed the larger solar system.  Your instructor is fishing for you to compare the gas giant systems to mini solar systems. He/she is also asking you to evaluate  differentiation between the smaller orbital radius moons and the larger orbital radius moons (more lighter elements further away from the central mass, because the nebula was cooler out there).  I think this is a weak argument, but it has some ammo if you look closely at the Galilean satellites. Ultimately,  the radial temperature profile  in the proto-Jupiter nebula is not necessarily the biggest factor in differentiation, however probably played some role.